Acorn TV

Depends on where you want to transfer it to exactly.

If by Apple TV you mean the actual black device that connects to your TV, you can sign in with your Acorn account into the Acorn App on the Apple TV. (Apple TV HD and Apple TV 4K only)

If you mean you want to transfer it to the Acorn channel in Apple TV app (the application now in may devices), then no, you cannot do that as explained by vazandrew above.

That is not possible. The Apple TV Channel version is a separate subscription. You would have to sign up directly through the TV app, but you would be entitled to a new trial. If you view that service solely through the TV app then that is an option to consider. However, if you view the service through other platforms as well then it would be wise to keep the existing subscription.