How to tell a girl that you want only to stay as friends?

You're entirely off on 'cuddling'. Cuddling can be done if two people are not dating, friends can do that. At least, it's pretty damn normal here. I cuddled with a couple of girls that were close friends, but we're not dating. Also, when you meant 'sleeping', instinctively, my reaction was of course 'intercourse', so I responded in the sense that you meant so.

Nah. When I think "sleeping together" I usually don't think anything sexual about it.