FAQ

An in-universe explanation; As Dr. Wimmer says, it appears Jason has unique regenerative capabilities. It's possible once Freddy resurrected Jason, he remained alive, consistently for several years, including when he'd been captured. Which gave him time to regenerate some of his skin and hair. Whereas, during most of the films, he's killed or otherwise incapacitated in some way that prevented him from regeneration.

Behind the scenes explanation is that it was likely a combination of budget limitations and artistic choice.

Pretty much all of them. Except Kane Hodder (Jason) and Yani Gellman (Stoney) who are American. Peter Mensah (Brodski) was born in Ghana, raised in London, but moved to Canada many years ago.

After Freddy vs Jason. In that film Jason is ressurected by supernatural serial killer Freddy Kruger after being sent to hell at the end of Jason Goes to Hell and eventually defeats him and emerges triumphant from Crystal Lake. He is then captured by unknown parties and is being held by the military at the beginning of this film.

Unknown, it may have been the military themselves although other suggestions have included Tommy Jarvis (from the fourth, fifth and sixth films) or Jason's niece and her boyfriend from Jason Goes to Hell.

It's possible Jason was left in a weakened state after his battle with Freddy and was apprehended shortly after. Seeing as how Freddy sliced off the fingers on Jason's right hand and Stabbed him in his eyes, leaving him partially blinded. The authorities would have had an easier time subduing him.

So far, there are 12 movies in the Friday the 13th series. Beginning with Vendredi 13 (1980) (1980), following are Le tueur du vendredi (1981) (1981), Vendredi 13 - Chapitre 3: Meurtres en 3D (1982) (1982), Vendredi 13: Le chapitre final (1984) (1984), Vendredi 13, chapitre 5: Une nouvelle terreur (1985) (1985), Vendredi 13, chapitre 6: Jason le mort-vivant (1986) (1986), Vendredi 13, chapitre 7: Un nouveau défi (1988) (1988), Vendredi 13, chapitre 8: Jason à Manhattan (1989) (1989), Le châtiment de Jason: Le vendredi infernal (1993) (1993), Jason X (2001) (2001), Freddy contre Jason (2003) (2003), and Vendredi 13 (2009) (2009). A fan film, The Cold Heart of Crystal Lake (2003), was also released in 2003. A documentary about Jason, His Name Was Jason: 30 Years of Friday the 13th (2009), was released February 10th 2009.