What versions does Bridge Glitch work on?

If you mean the Prawn Island bridge, than it works on all versions that exist.

What's the fastest versions?

What do you mean exactly? The glitch can be executed just as fast on all game versions

I mean in general,what has the fastest load times between Platforms?

PC, a couple of frames at most on a decent PC

Aw Shoot,I got a PS2.

Is there anything to know about starting to Speedrun this game?

There are many things to know, but it depends on how seriously you plan on taking the game. PS2 is much slower than PC, and not a lot of people play it.

Most of the game's guides are based around PC speedruns, but if you wish to stick with console you can watch the guide and compare it alongside a PS2 speedrun to see how things are done differently on console.

The prawn island bridge thing ackshually doesn't work on the Xbox version