Anything unique about RE2 for N64 over the Gamecube RE2? Because you can just inject the Gamecube version.
They're completely different versions.
The Gamecube port is a straight port from the PSX version (I believe the Dual Shock version).
The N64 had different extras from the PSX one.
For one, Extreme Battle is not included, and good riddance, I never liked it lol
The N64 has some additional files you can find throughout the game, called EX Files, which further cements and connects RE2 to other games, and I believe even RE Zero (which was in development at the time). I think it also had cheat codes for Infinite Ammo, Infinite life, etc, which you could enable by making some button combo in the Load Game screen.
Also, the N64 had some new costumes, and a completely new (optional) control scheme called "First person controls", and guess what those did?
They got rid of the tank controls, making the character move to wherever you hold the analog stick to.
Hold it right, character goes right straight from a standing point, you no longer have to turn the character slowly to move to a 90 degree angle, you can do so straight from standing still. Of course these were optional controls, and you can always choose the original tank controls as well.
The N64 version also had blood colour options (green, blue, red), violence settings (low, medium, high) and once you completed the game, you could enable a whole new complete Randomizer option in the game, which completely changes which items you find throughout the game (this doesn't apply to key items).
As you can see, it had quite a good amount of stuff to its favor, much more than the lameish Extreme Battle mode from the PSX imo.
It also had better graphics compared to the PSX version, but the N64 had some compressed audio and FMVs, but that's about all the cons to the N64 one.