From the notes, I understand that you are unable to restore your RDS snapshot as you are unable to select some options. Please correct me if my understanding is wrong.
As a workaround to your issue, I recommend to try using other tools like RDS API or AWS CLI to perform the restore. Below is an example of AWS CLI command to restore from the snapshot
aws rds restore-db-instance-from-db-snapshot
--db-instance-class db.t3.small Please see the documents in links ,  for steps and how to use AWS CLI as well as RDS API for restoring from a snapshot. I hope the above information is helpful.
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