How many times can i reinstall windows 10, without getting problems?

On the same PC? There is no limit that I am aware of, it should pull the license from Microsoft automatically since it's the same machine.

The question I have is WHY? If you need to restore Windows back to "stock" after some experiments or tasks or something then there are far better ways.

I've used Macrium Reflect for this type of thing. There is a free version and the paid version is well worth it. Get your installation the way you want it and create a backup to another disk or USB drive. If you need to get it fresh again, open Macrium and restore it. It tales minutes to do and if you get your drivers straight on the backup will save a lot of time and effort in the long run.

/r/Windows10 Thread