I'm not sure it would work to put fresh mango into the freezer, I think the frozen stuff if frozen rapidly, so as not to make it mushy. Might be worth a try with a bit though, nothing to lose but a few pieces of mango!
I love mango - There's a trick to cutting it though: Cut one of the flatter sides off, getting your knife close to the stone. Then on the piece you've cut off, slice into the flesh, up until the skin into diamond patterns. Then push the underside of the skin so the diamonds pop out, then just cut them off. Once the other side is done there's only a bit around the edge of the stone to cut off.