I have a few questions regarding moving a wallet from a laptop to a usb

1) Do I need to be logged in (unlock a wallet) to backup... to save the dat.file?
2) what happens to the wallet on the laptop when i save the dat.file? Can I still access the coins on my old laptop later?
3) In general, it would be nice if anybody can tell me the steps LAPTOP --> USB-Stick --> NEW LAPTOP in words and if there is a youtube video which explains it very well.

Thank you!