The rules section says there is an autosplitter for this game? is there? if so, where can i find it?

On the discord, click on the link on the side :D

Is it mandatory for me to use an autosplitter, or just recommended?

You should use it, it's 100% accurate, but it's like you want

https://www.speedrun.com/zd/guide/f3r6q and https://www.speedrun.com/zd/resources

Is where to also find it.