Install lower iOS on iPhone 4S upon activation?

Ok, so I got a replacement phone in the mail, and basically what I'm wanting to do, since I already know 4S can't downgrade or be jailbroken on 6.1.3, can I install a lower iOS like 6.1… Or anything else if I get the ipsw. It download for it. I know where to get them, but is it possible for me to install a earlier iOS so I can jailbreak it instead of installing 6.1.3.

Nope. You can't downgrade.