It is correct and would be perfectly understood, but a more American flow would say this: When I get back home, I'm going to take a nap. English speakers use the word "get" frequently when they want to express the concept of arriving somewhere or going somewhere.

It is correct, if the speaker is still at home when she says it, plans to leave and then return. If the speaker is not at home when she says it, it should be "I plan to take a nap when I get back home" or "- go back home"

I'm going to take a nap when I get/come back home. Use "come" when you are coming to the person you are tlaking to. Otherwise use "get".

I take a nap when I return back to home I have a nap turning back to home. I nap for a while after returning to home.