Below is a guide on what skips, tricks, and glitches are possible in each version of the game, and goes over the general visual and mechanical differences between versions. Although there are more than 5 versions of the game that have been released, there are 5 "versions" just to identify the major differences.
Spreadsheet Link: https://docs.google.com/spreadsheets/d/1m1MqzghLq8R1M_DQYwR1-7DwxgWMaxfaaVkc2HOLKwc/edit?usp=sharing
As a summary of everything you need to know for speedrunning:
When not accounting for Infinite Jumps and Major Room Skips, which are banned in speedruns, V. 5.0 is the fastest version of the game to run on assuming you do all of the strats. If you skip out on doing some of the more difficult strats then don't worry, your run will most likely neither gain or lose time between versions. If you're curious, V. 5.0 is estimated to be 20 seconds faster in Any% and 100%, and 0 seconds faster in Any% NG+. You can easily determine that you're on V. 5.0 if you own the game on Steam or iOS, assuming you're up to date, and you can double check by seeing if you have save slots when loading up the game. If you are on the latest Android version, then you are on V. 4.0. The only time you may be on V. 1.0 through V. 3.0 is if you're running a pirated copy of the game, so just... don't.
In addition, if you want to try out these other versions for whatever reason, you can download them using the link below. Don't worry, this isn't piracy. It will only boot up if you own the game already.
