this will vary with different institutions.. If you deposit money into an account you will have access to it instantly with most banks, unless they don't do in office processing or have some sort of memo credit system in place. I can't think of many that don't. Credit unions aren't available to everyone tho and are still limited in lending as opposed to any fdic bank.
2. Credit unions are insured by the NCUA, a federal agency backed by the full faith and credit of the US Government just as the FDIC, and in the same amounts with the same rules about accounts.