could be mistaken Mat but i think all the 34 non turbo's came with 25gt on the back, so if yours is a normal 25gt then no it doesnt have the upgrades of a gtv, and no it doesn't have an lsd, one way to confirm althought not 100% accurate if some1 has changed them for whatever reason is to check if you have 4 piston fronts and 2 piston rears (found on gt-v's).
and for the badges on the guards (red/blue), those can easily be swapped.
as for the gt-4, once again im not sure but i think they only came in 4-door? can some1 confirm???