How high of a regen. Like Wolverine down to cell regenerating from a drop of blood leve? Gurren Lagann "create things out of nothing" infinite regeneration
Not in base form. He can regen while it's suffered a lot of damage (like losing limbs), but not quite to that extent.
Regen's fast, though; it was back to full repair in the previous lost-multiple-limbs instance in a couple of seconds. And yes, it can be used in base form.
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"As the size of an explosion increases, the number of social situations it is incapable of solving approaches zero." -Vaarsuvius, Order of the Stick