Can we set up a recurring donation payment?

Also want to know if I can set up the frequency (for yearly donation pledges, i.e. charge the same amount once a year if agreed)

The answer to this one would be both Yes and No. The reason why both are the answers is because you can set up a recurring payment, but you can not do it for the donations.

So instead of selecting donation, you would need to set up the form to sell subscriptions.

You can see more about that here: How to setup a recurring payment option

Now since you want to accept custom donations as well, it might be possible to have both - but the user would need to select which one of the two they would like.

This is done by creating one parent form and two child forms - one that is able to accept custom donation and the other that is selling subscriptions.

You can see how to have both (on the same form, but not in the same time - only one can be used at a time) here: How to Create a Basic Multiple Payment form

Do let us know if you have any further questions.