If I already have some Lazarus versions installed when FPC stable was 3.0.4 and I later install FPC 3.2.0 or 3.2.2, can I then change the compiler to use for the older Lazarus versions to the new Fpc?

If I look at the Lazarus Tools/Options/Environment/Files I see items like:

Compiler executable: /home/pi/lib/fpc/3.2.0/ppcarm FPC source directory: /home/pi/dev/fpc/3.2.0

Can these be changed to point to the new FPC so the old FPC is no longer needed?

Or do I have to keep the old FPC compiler around when I update it to a new version?

Bo Berglund wrote

Can these be changed to point to the new FPC so the old FPC is no longer needed?

Usually yes, FPC usually is backwards compatible. But there can be some glitches. I would update Lazarus along with FPC a well.

Anyway, you can always check if everything works with the new FPC version and if yes, only then delete the old FPC version.

Ondrej