Early on, Merryweather expresses the desire to turn Maleficent in "a fat old hop toad". The others chide her, saying that it's impossible because their magic can only be used to bring happiness. Merryweather gripes "Well, that would make me happy". During the climax, the fairies never attack Maleficent directly, instead essentially buffing Phillip and his gear. Presumably it's because of this happiness thing, which makes their magic useless for direct offense. Yet Merryweather is able to turn Diablo to stone. Why? Because doing so certainly made her happy.
Aurora and Phillip's love at first sight makes a lot more sense when you remember that part of the curse Maleficent placed on Aurora as a baby was that she would be "beloved by all who know her" and that Merriweather's gift requires true loves kiss, there fore there needed to be true love in place.
The story takes place in the early 14th century. Now what happened in the 100 yrs Aurora was asleep? The Plague. Merryweather saved Aurora from the plague.
Only in the original Tales and Ballet, in the Disney version, it could be no more than a couple of days, so yeah...
The fairies constantly tell Aurora/Briar Rose to not speak to strangers. Although she hits it off with Philip in the forest, note what she does next. She leaves and makes arrangements to get to know Philip better - not in the forest but in the safety of her home where her 'aunts' would be present. Quite a clever girl.
In the original story, Sleeping Beauty is asleep for a hundred years and her entire castle and servants were put to sleep too. How would that feel for the servants to wake up in a new century with nothing left of their old lives anymore, just because a magical curse wanted the princess to have some hired help when she woke up? Think about it, they wake up and find that everyone they know outside of work is dead, the world is now foreign to them, and they lost everything solely because the fairies wanted them to continue working for this one princess.
In that era, odds are that their entire lives were in the castle, or at least the town that was most likely within its outer walls.
That was the case and was lampshaded in the Twice Told Tale book A Kiss in Time. After the curse is broken, most of the people in the castle think that a month has gone by at the latest, when centuries have passed. Towards the end of the book, when the protagonist (a boy from modern times) interrogates a lot of the peasants living in the town, most of them still had no idea that any time at all had passed.
The movie Maleficent planned this as an ultimate punishment for Aurora and Phillip as she planned to keep the latter in her castle for a hundred years, letting him go to the princess causing her to Go Mad from the Revelation once she realizes that she hasn't aged a day.
It's more likely that Maleficent was speaking euphemistically, planning to keep Phillip in her dungeon until he died of old age - the animation that accompanies Maleficent's speech shows both Phillip and his horse as transparent, as though to indicate that they will only be leaving as ghosts, and it's highly unlikely that Phillip would still be alive after one hundred years. (His horse certainly wouldn't be; they do well to live as long as thirty years, never mind a hundred.)
It's easily within her power to keep both of them alive indefinitely, even if she does mean a literal century. And Maleficent's curse would be broken eventually, so why wouldn't she make her triumph complete by reuniting the two lovers in such a way that they could never be happy?
Why didn't the people just tell the princess about the curse in the original version? To me it seems like that could've saved them a lot of trouble...
They maybe thought that would make her end up afraid of everything. It seems that they were sheltering her.
In the Disney version, the good fairies are capable of many feats of magic, yet when they sneak into Maleficent's stronghold of the Forbidden Mountain, they don't turn themselves invisible (like any faerie would). This could be because Maleficent might have enchanted her orc guards to see invisible things, but had she done so she probably would have invested a lot more in them, including the intelligence to look for an aging girl over the past 16 years.
Or, more simply, the fairies just can't turn invisible. They're never shown to have that power at all. Maleficent seems to be able to become intangible or diffuse into the aether, but, then, she has power gained from Hell itself, and her magic far exceeds what the good fairies are capable of, so it's not surprising she can do something they can't.
Maybe they can but an invisibility spell must be maintained - requiring a lot of concentration. The fairies need to bust Philip out of the mountain so they need to save their powers.
No one in the film seems to realize the entire story could have been avoided by just waiting until after Aurora's 16th birthday to re-introduce her to her parents and royal life.
The original ballet actually addresses this. Aurora is never removed from her home, and is instead raised with love (and presumably without the presence of sewing apparatuses). On her 16th birthday, she is given a coming of age ball, complete with suitors. Carabosse (Maleficent) crashes Aurora's party, in a Paper-Thin Disguise, and gives Aurora the spindle in person as a present. The spindle is either disguised (for instance, hidden in a bouquet of flowers), or just handed to her. From there, the story relies on Aurora being only 16 and acting like an excited teenager. She rushes over to show her parents her new and mysterious toy, then dances away from them when they try to take it away from her. (It's my present!) And then promptly pricks her finger as Carabosse does her "I told you so" ritual, and the Lilac Fairy shows up to give the hysterical kingdom a massive sedative.
Actually hiding her was an invention of the Disney film, where the blame can probably be laid mostly on King Stephen being really impatient to get his daughter back - the fairies were waiting until the sun had set to actually present her, but in order to do so as soon as the sun had set meant bringing her back to her father's castle earlier in the day. Learning that she'd fallen for (they thought) some random guy in the forest and was planning to meet him that night probably helped in the decision to go ahead and leave the cottage, too. Either way, as far as the Disney film is concerned it's not like waiting a day would have helped - Maleficent knew where the cottage was by that point, so if they'd stayed there until the day after Aurora's birthday, she'd still have shown up there (in fact she does show up there, which is how she captures Phillip).
If the fairies are so incompetent at things like sewing and cooking, even after sixteen years of living as humans (Fauna has apparently never cooked, according to Merryweather), how have they survived for that time? Aurora's never met anybody, and it's not like they can get Amazon orders out there. Where's their food and clothing coming from?
By the way Merryweather seems surprised, I'd say either the roles are usually reversed or Merryweather herself usually does one of those jobs.
When Flora announces their plan, Merryweather says "but I've never baked a fancy cake" to which Fauna replies that she'll be cooking. That seems to imply that Merryweather did the cooking. It was presumably very basic so Merryweather has limited knowledge of the kitchen from sixteen years. Perhaps she or Fauna sewed Aurora's dresses too. Since it's the last day, I got the impression the fairies were switching up the jobs and doing what they'd never done before for fun.