Tester indicates hot/ground are reversed after lightning strike
Somewhere in your house wiring a neutral line is disconnected / broken / melted. You will need to open every electrical box and check the connections and splices. If you don't find anything there, do continuity tests between junction boxes. If the fault is between boxes you may need to open the walls up.

Your GFCI outlets are almost certainly dead. Any overcurrent big enough to sever a wire will fry a GFCI. Just replace the lot.

"Hot/Ground Reversed" isn't testable without a third connection. There should be full voltage between hot and ground - if not then you have an open ground. If you put a meter between ground and a known-good ground (like a metal water pipe) and see full voltage then you really do have hot and ground reversed (and a major problem - call an electrician).