Q: I changed apple ID,  and passwd, but the icloud keeps the old apple ID and it doesn't let me sign out/in?

If you can't log out due to being prompted for the previous id/password try : If iCloud asks you for the password to your previous Apple ID - Apple Support

When you change an id and/or password (when changing an id it's generally best to logout everywhere first, then update it, and log back in with the updated version afterwards) : What to do after you change your Apple ID email address or password - Apple Support