Upgrade A4 device from ios 4.x to ios 5.x?

I just received as a gift this iphone 4 as with ios 4.3.3 on it. After reading from various sources, I understand that once I upgrade, I cannot ever revert back. Next, I do not want to have ios 6 on it, but version 5 instead. There is no additional software installed on the phone, so I do not care losing anything when erasing it with "restore" option. If I manually download the latest 5.x firmware, will itunes happily accept to perform a shift-restore with it? Or will it only allow ios 6 ipsw?

Thanks.