You can downgrade the firmware that way, but any baseband updates that are installed (on an iPhone) are there forever - you can't downgrade to a previous baseband that is jailbreakable/unlockable.

This is only relevant to iPhones, since it just means that you can't use earlier unlock tricks to unlock more recent basebands. You can still jailbreak, though.
If it's brokenless, don't suffix it...