I already post you link from wikia.
so if you didn't read it,

JEM555 is actually much better then the
Jem Jr which is usually JEM333,

so JEM555 do not need junior (Jr) designation,

JEM 555 is produced 1994-2015, I do not understand why you insist that guitar has to be from 1994,


with age, clear coat exposed to light start to yellow,
so a lot of white guitar with years become cream,
( blue become green or similar),

some manufactures,
like Ibanez with Jem guitars,
use uv-resistant clearcoat to prevent yellowing,
so your guitar is fine

neck is not Prestige, it is most likely original Jem555 neck with half tree of life, like suppose to be,

and white pearloid pickguard is correct as well,

pickups should be Dimarzio evolution like on prestige JEM,

and if you want to change tremolo, replacment is edge pro, ( this is edge pro 2).