GBA Info
Super Mario Advance 3: Yoshi's Island is the port of Yoshi's Island to the GBA. It's a very faithful port but it does have some differences like minor level changes, new sound effects, and unfortunately, a lower screen resolution.
Most importantly due to it being a new system, there are differences in how some glitches that corrupt memory work especially OAM overflow and Out-Of-Bounds wrong warps. This leads to GBA having unique speedruns that may be interesting.
Note that this is under investigation and information may change and this is still not fully understood
Relevant Glitch Differences
Tongue Glitch can not be achieved at save rings in the same way but can still be done with toadies. However tongue glitch does not boundlessly create OAM entries causing memory corruption.
Null Egg is still possible but the majority of sprites crash on goal entry and as of now, there is no known way to bring a null egg out of level. There's also some unique stuff that can happen when carrying a null egg.
Goal OAM Overflow Corruption (unlocking new levels)
On the GBA version of Yoshi's Island, following the OAM tables (sprite graphic entry data) is data for the current played level ID (IWRAM: 6288) and current World Map Cursor (IWRAM: 633E). This means if you overflow the OAM table with enough sprites, you start writing arbitrary data into these addresses and on level completion can end up on other level tiles on world map (including glitched worlds/levels).
This is usually done by gathering a lot of enemies at goal ring, using a cloud item to turn them into clouds and then entering the goal at the same time. This causes too many sprite graphics loaded at the same time which goes past the normal table and corrupts World Map data.
Wrong Warps differences
GBA doesn't clear previous screen exits from levels you visited so wrong warping can bring you there. This means if you previously played a level, even from another file, you can warp to those exits. This also means doing runs that utilizes warps need to do it from a hard reset to avoid warping to already completed exits.
Out-of-bounds warps read into current screen VRAM table so it can be manipulated into going different exits depending on what graphic tiles are available to load.
World Records
Somebody has done it