You must remove from play at least 1 Rock-Type monster in your Graveyard in order to Special Summon “Megarock Dragon”.
If you Special Summon “Mega-Rock Dragon” with an original ATK of 2100 points, and you equip it with “Megamorph”, its current ATK will become 4200 or 1050 depending on your Life Points.
If “Skill Drain” is active while “Megarock Dragon” is in play, the effect of “Megarock Dragon” is negated and its original ATK and DEF are treated as zero. Even if “Skill Drain” is destroyed later, the original ATK and DEF of “Megarock Dragon” will remain zero.
If “Megarock Dragon” is flipped face-down, or removed from play, or sent to the Graveyard, its effect is wiped and its original ATK and DEF are zero.