I withdrew money from my 401k due to financial hardship, the institution in error sent to a closed/overdrawn account (I have proof this is their error). Can the bank legally take my money even though it was for hardship and they were previously notified of bankruptcy?
They wouldn't be able to take your money, anyway, given that the error was on their part. The commencement of your bankruptcy case strengthens your protections.
No. Not unless it happened before the bankruptcy filing or they have received relief from the stay after the filing.
Possibly. It depends on the timing of how it came down.