since its technically n64 graphics, i honestly wonder if u can port it to the wii

This is a fascinating idea I know nothing about, and I do hope you get an answer.

just because it is n64 graphic does not mean a wii can handle it

Id give it a try if you can, im curious now too lol

When you write code for those old consoles, you have to build an entire engine from scratch using nothing but the SDK for the console, it's usually only worth the investment if you are planning on building a company around that and releasing several games.  Celeste, like most indie games, is built using an existing game engine.