2019-07-12 : If the target Elemental is an illegal target by the time Omnath’s second ability tries to resolve, the ability doesn’t resolve. You don’t draw a card if you control eight or more lands. If the target is legal but can’t have a +1/+1 counter put on it (most likely because an opponent controls Blightbeetle), you do draw a card if you control eight or more lands.

2019-07-12 : The number of Elementals you control is counted as Omnath’s first ability resolves. If Omnath is still on the battlefield, it will count itself.

2019-07-12 : You may choose Omnath as the target of its own second ability.