This sounds like it would be a category extensions run. https://www.speedrun.com/pkmnyellowext
For category extensions runs mods are generally willing to add the category if someone has a completed run of the category they want to add with a rule set in mind. Also not really sure if you are saying you want to do a glitched run with a level 100 starter patched in, or if you mean like a category where you have to get a pokemon to level 100.
If you are looking to do a modded run with a patched in level 100 starter its questionable if that would get on the boards due to being a modded game so technically not pokemon yellow at that point.
I will say I know in red you can do a glitch to get a lvl 100 pokemon really early on, and something like that would be allowed, but straight up patching or modding the game to get it wouldnt be.
a glitched run with a lvl. 100 glitch that works in PKMN YELLOW. i catched a lvl. 100 Nidoking, but i not screenshoted or recorded bc i does this glitch just to test and bc my device crash the game when i do screenshot.
