Rising Miasma

If the non-awaken part of the spell doesn’t require a target and you cast the spell for its awaken cost, then the spell won’t resolve if the target land you control becomes illegal before the spell resolves (such as due to being destroyed in response to the spell being cast).

If you cast Rising Miasma for its awaken cost, creatures will get -2/-2 before the land you targeted is turned into a creature. Unless it was already a land creature before Rising Miasma started resolving, it won’t get -2/-2.

You can cast a spell with awaken for its mana cost and get only its first effect. If you cast a spell for its awaken cost, you’ll get both effects.