Pretty similar to N64 games (Mario, OoT, MM) or gamecube games (Mario Sunshine). Speedrunners have modded consoles or hacked ROMs for tricks/glitch execution practice.

This is really helpful for practice. I would love to know if it is possible to do this on PS1/PS2 consoles and if it already has been done on those consoles, which games have practice cheats.

Also asked on reddit: https://www.reddit.com/r/speedrun/comments/7lsvvg/are_there_any_ps1ps2_speedruns_that_use_cheats/