Why does Jason bother to cover his face at all? He used a potato sack (or whatever it was) in the first couple of films, so it clearly was not for Rule of Cool (not that a maybe undead, psychopathic murderer would/should care about that anyway). His sole purpose in life seems to be to terrorize and/or kill anyone 13 or older that he comes across— his hideous mug would be great for doing the former (as seen in Jason Takes Manhattan). There's no chance he's THAT sensitive about his physical deformities, is there?
Looking for anything resembling genuine characterization in the series is a mostly lost cause, but there are occasional signs throughout the series that at the end of the day, Jason Voorhees is an angry, cruel ten-year-old boy in the body of a seven-foot-tall immortal serial killer. He's actually reasonably sensitive about his disfigurement, to the point where he may wear the mask so he doesn't have to look at himself.
And "Jason Takes Manhattan" has him show he knows how ugly his disfigured face is, considering he lifts his mask to scare away some guys bothering him because he didn't have the time to kill them.
Yes he is that insecure about his looks. It's a hold over from when he was alive and whatever caused his mental handicaps also left him deformed as a human and children can be cruel. In addition everything we've seen about his origins are at all true the camp counselors were typical teenage pricks and probably gave him more than his fair share of shit.
Where does Jason keep getting new outfits? In many of the movies (especially the first few) Jason has a completely different set of clothes to the last one. Does he go shopping or something?
Out of Verse because keeping realistic clothing damage between multiple films would be nearly impossible, it's probably supposed to be the same outfit and the props department didn't give a shit. It's hard enough to keep things consistent in one movie. Inverse Jason is larger than your average male but not monstrous. It's not difficult to believe that he's able to scavenge enough clothing from the two parks (Crystal Lake and whatever the neighboring Camp from Part III) and the surrounding city. It's not entirely clear how far Jason's territory extends and he only seems to change between flicks which other than the first few films are implied to be years apart, usually long enough for the notoriety of Jason to die down some. A few years is more than long enough to grab one or two outfits and Jason is shown to be clever enough when he needs to be.
In the original: If Pamela Voorhees' ultimate goal was to stop the camp's re-opening... Why didn't she just kill Steve and be done with it (Other than the obvious "She's insane" handwave)? No yuppie funding, no camp revival.
It's probably not just about closing the camp, it's also about sending a gruesome message to neglectful councillors everywhere. Also,keep in mind Pamela's a vengeful sociopath who blames the entire camp for her son's death. Just listen to the speech she gives Alice. In her twisted mind, everyone associated with Camp Crystal lake is guilty.
When and how does Jason age? He goes from a skinny teen in the original to a hulking adult in the sequel almost literally over night.
Jason in the original was Alice's hallucination/dream. She never saw him and imagined what she assumed Jason looked like - a zombie kid in the lake. The sequel reveals that he was actually alive all along and had over two decades to mushroom into a hulking man. What's really wierd is that in these years he apparently has never bothered to inform his beloved mom he was, in fact, alive.
In the second movie how did Jason manage to track down Alice? Did he just look her up in the phone book?
The expanded universe explains her house was at or near Crystal Lake, her having moved there to confront her trauma. Jason could easily have seen her walking around some day and recognized her (as it's also offical he saw her kill Pamela).
In Part III Jason is shown attacking Chris in a flashback with a knife. However after he loses it he just keeps chasing her and then... she wakes up at home. So... what did he do to her? He obviously neither killed nor mutilated her and, considering that it's Jason, it's unlikely he raped her either. Did he just drag her around the woods then dump her when he noticed she'd passed out? Why?
Well, Jason has always been a rather territorial creature. Maybe he had found her trespassing on "his" turf and just wanted her off of it.
Since Freddy and Jason are in the same universe, what happened to Freddy Krueger when earth one was destroyed in Jason X? Does he forever roam around in dream world since there are no earthlings to terrorize and kill?
Freddy and Jason are not in the same universe. Freddy vs Jason, like Alien vs. Predator takes place in its own continuity. However Freddy has shown in the past to be quite the rules lawyer when he needs to be. The most likely answer is that he either hitched a ride in someone who was descended from the Elm Street kids. Or even though the ships we see in Jason X are named after monsters that could just be that batch and somewhere there's a batch that were named after trees. A nightmare on Elm ship is the exact sort of thing Freddy would find hilarious.
That, or someone had the spectacularly bad judgment to name a ship after Freddy.
I don't see why Freddy vs. Jason wouldn't be canon. As for Freddy, he's presumably either stuck where Elm Street used to be, or stuck in the Dream World or Hell, unless he somehow found a way off of Earth.
In part 2 Jason was strong but not insanely strong, his killings were mostly by element of surprise and in the end struggled to subdue the final girl's boyfriend who survived the fight. Come the next movie that supposedly takes place mere days after, he is suddenly strong enough to not only dispatch everyone with easy, but at one point he squeezes a guy's head so hard his eye rockets out of his socket. On top of that Jason was heavily wounded at the end of Part 2, so, if anything he should be weaker here. He also somehow grew much bulkier between movies, but that can probably be chalked up to The Other Darrin. I wonder specifically if there can be an in-universe explanation for this, since I know the real one.
Adrenaline? Or maybe his rage at being injured supplemented his strength?
Even after umpteen movies and umpteen - 1 killing sprees, how do the characters in these movies STILL not know who Jason Vorhees is?
You're overstating the movies. Friday the 13th 2-4 take place over what appears to be a single summer with 2 and 3 being directly back to back. Friday the 13th 5 doesn't actually feature Jason, the villain that time is the father of a mentally disabled teen who is killed in the first act. 6 features his revival as a zombie (or whatever he is) and takes place years after the first four movies with an adult Tommy. Much of that movie hinges on the locals do know about Jason. He's a dead serial killer who up until then had shown no magical powers at all. Seven has little excuse, eight is takes Manhattan and features kids on a cruise. They weren't even at Crystal Lake for most of the time and that is where he's supposed to be. Nine (Jason goes to Hell) they know exactly what Jason is and send the FBI and if not for a serious case of Powers As The Plot Demands that would have worked just fine on Jason. Ten (Jason X) takes place centuries into the future and clearly real monsters are sufficiently rare that they didn't really believe he could come back from the dead. Freddy vs Jason involves Jason being where he doesn't belong, in a city that has it's own monster who can only attack in your sleep. It's immediately clear that the police (and probably most of the adults) have concluded that Freddy is back again and dismissed any facts that disagreed with that. In fact they would have been wise to blame the murders on Jason. He's something you can shoot and it would have prevented Freddy from returning. So in closing out of eleven films only 9 feature Jason. Of those 9 four of them take place away from Crystal Lake. 2,3 and 4 are all one long spree that ends with his death. 6 is his revival after more than a decade leaving just part seven as a legit what the hell.