OpenAthens is a username and password system. It lets websites know which Trust you work for - and if we subscribe to their content, they will let you access it.
No. Just because you see an "OpenAthens login" option, doesn't mean you can access it - we need to be a subscriber to that resource.
If possible, register using an NHS email address, or using a computer on an NHS network (this means your eligibility can be checked automatically, and your account activated immediatedly).
No. You can take your OpenAthens account with you if you move Trust - just log in and alter the Trust you work for in your account.