What happens after 30 day trail?

Does the Unity Pro 30 day trail automatacli go to the free version efter 30 days? or du you have to download it?

I believe the installation is the same so you don't need to reinstall it but you have to request a (free) basic license key through the unity website and use the Enter Serial Number menu to enter it.

you just need to activate your unity another time with a free license.