After you surrender your plates, your Receipt FS-6 T indicates if you are eligible for a refund. If you are and you do not request a transfer receipt, your refund will be processed automatically and you'll get it in your mail after some weeks.
Can I still apply for a refund if the registration sticker was attached to the plate?
No, in that case, the sticker can't be removed and you won't be able to apply for a full refund.
What is needed to apply for the 2-year refund?