i applied for 4 visas at once at the singapore embassy to get the non-immigration marriage visa.

when am i supposed to create that 400K bank account? Each visa is 90 days. If I create the bank account, how long am I allowed to stay? Do I have to report?

1. Was not aware Singapore, or anywhere else, was currently issuing 4 entry non immigrant O visas. Are you sure it does not say "multi"?

2. You apply for an extension of stay after you meet the requirements; over 400k in bank account. It should be done during the last 30 days of any 90 day entry.

3. The extension of stay is for one year from your last date of entry.

4. You are required to do 90 day reports of address after you are here 90 days without leaving. So you do not do on visa entry stay but only after you extend your stay. The day you apply for extension of stay at Immigration is considered your first report so the next will be do 90 days later.