Jason Voorhees and Leatherface are not in GTA San Andreas normal gameplay. They are just two more myths to add to Bigfoot and Aliens, etc. To produce this kind of thing you would need to have a mod (via a computer). Suggest you have a look at the modifications section of the gtawiki site.
Jason Voorhees does not have a middle name.
Jason Voorhees is Jason's full name.
The surname of Jason, primary antagonist of the Friday the 13th films, is Voorhees.
Jason Voorhees wears a goalie mask.
No. Jason Voorhees is a fictional character.
Yes, Jason Voorhees is a male.
Elias voorhees
Jason Voorees is a fictional character.
No, Mrs Voorhees was Jason's mom before she was killed.
Jason Voorhees is a fictional character. He does not exist in real life.
No, Montgomery is not the middle name of Jason Voorhees. Jason's full name is Jason Voorhees, with no known middle name. Montgomery does not appear in any official sources related to the character.
Yes. Jason Voorhees has been used for several novels and comic books.