Andy's and Karen's names were cleared during the events of Seed of Chucky.Why else would they do a Movie Within Movie about Chucky being the killer without any mention of Andy?
The reason Tiffany joined back up with Chucky in Curse is because...After his arm killed human Glen (and probably human Glenda too) Chucky's head convinced Tiffany that the two of them were better off without kids because now they could spend more time with eachother. Cue their set up in Curse.
The reason an army of Chuckys wasn't created at the beginning of 3 is because the Demballa spell has a one vessel limit.So that's why only one "Chucky" doll was created from a whole batch of blood infused plastic.
Tiffany tipped off Andy.She was still pissed at him for the events during Seed of Chucky so she played his game until he was delivered to Andy.
Nica died after she had her heart attack.The rest of the movie is her in Hell. Think about it, after she has her heart attack, she's almost never mobile. First, Ian has her hands strapped down so she can't move the chair on her own, and then Chucky throws her to the first floor through the banister, which caused her wheelchair to break. Then later, at the end of the film, Nica is found mentally unfit and is condemned to live in an asylum for the rest of her life. Seems like hell, right? Also, as Nica faints from her heart attack, we see Chucky approaching Ian from behind. Yet, we later see that Ian moved Nica from the garage and didn't even notice Chucky. Why would he approach him from behind if he wasn't going to do anything?
The Tommy Doll was actually John the Voodoo man.He wanted to keep a close eye on Andy and was willing to go against his religion to do it. He was not able to fully transfer his soul into that one, but enough so he could move around instead of speaking verbally to warn Andy. Hence why he was standing at the end of the stairs like he was waiting for Chucky.
The reason Chucky doesn't bleed in Curse, and also the reason he doesn't need the Heart of Demballa to transfer his soul into Alice is...He has a new body. It's his old head from Seed, which got chopped off by Glen, but Tiffany must have put it on a new Good Guy body and since Alice is the first person he told his secret to with this new body, he can do the transfer without the amulet.
Everything after the hospital scene in Seed of Chucky is Glen's dream.Basically since the movie opened with one of Glen's dreams it only stands to reason that it should end with one too. In reality Tiffany, now in Tilly's body, took doll Glen home, faked Tilly's death and stole all her money, then ran away to start a new life with her son/daughter. Eventually she dyed her hair blonde and began acting like her old self again. She never transfered Glen/Glenda's soul into the babies because that would basically be like killing them and even she's above that, so she put them up for adoption instead. Tiffany and Glen/Glenda lived in peace and hapinness for many years until Chucky showed up again and talked Tiff into going along with the whole "special delivery" plan.
The reason Chucky is alive again between Seed and Curse is because the Hack/Slash vs. Chucky comic is cannon.'Nuff said.
Andy did NOT kill Chucky at the end of Curse of Chucky.If I recall correctly we did not hear any kind of gun shot, so one can assume that he did NOT shoot Chucky. There will be one final movie featuring Andy and could possibly be the end of the saga.