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.
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If it's brokenless, don't suffix it...