I was wondering if I ever need to collect any user data (for example, their location, which I don’t think I should collect now, their IMEI, their google account, usage time of the application, etc.) , then how much I can collect without doing it illegally.

I know that there will be problems with all of them, but since I could not find a single document or question about SO, referring to this topic, telling what data I can collect, I am here with a question.

Hope to get some good answers.

Wish to mark this as a community wiki.