[Question] Is there anyway to use the bootrom exploit on the iPhone 4 that was used in limera1n to downgrade it from 7.1.2 to any iOS version it supported?

I’m wanting to buy an iPhone 4 from a friend to jailbreak it (among other things), and I was wondering if this is possible before I buy it. And isn’t it technically possible, since bootrom exploits can only be fixed with new hardware?