Question about taking brake pads and rotor on and off

2008 infiniti g35 - I want to practice taking the brake pads and rotor off, do I need to still decompress the pistons or do anything with them? What I want to do is take everything off and put everything back the way I found it and I can't tell from the videos and forums I've looked at if you only decompress the pistons to insert new brake pads or if you need to do it regardless.

I'm using this car to practice maintenance work before selling it for cheap which is why I'm not replacing anything, this is purely to practice doing it.