rotom-h is hit super effective by stone edge 'cause he is part fire...Rotom-H and Rotom-W are hit neutrally by SE.
Mamoswine will be an event-only pokémon, and will come as a Mamoswine already.
So, unless they change the rules for it (male-only with level-up moves), Thick Fat Mamoswine cannot have Superpower, Stealth Rock, Curse, Icicle Spear, Icicle Drop nor Ice Shard. Yay?
Sadly, Mamo no longer has the 3rd strongest OU earthquake, he has the 4th. Dory has 5 more attack than him.
On Bulbapedia it says that the gender is unknown.