in that article you will find how to see if you have backups on different platforms, so you can do it on Windows,
even if you (if I understood you correctly) using different account on the iphone right now. Bear in mind that I saw somewhere that Apple reserves the right to delete any backups on account that haven't been used for over 180 days.
As far as what you can do is you can't just take pictures out of icloud backup. The only thing that you can do in similar situation is to backup your phone to computer or new icloud account. To restore from old backup and import pictures to computer. Then wipe phone again and restore back to current condition. Complicated, but the only way.