Couple of questions..

The first one is easy.

Does (Unit - Explode Unit) have the same effect as (Unit - Kill Unit), as in can exploded units still be revived through triggers?

The second one might not be so easy. Is there a way to count the level of all of the units in a certain unit group? I'm trying to find a simple way of detecting whether or not the total level of units in a certain unit group is above 1800.

1: Yes
2: Pick every unit in unit group and do actions.
Actions:
Set Integervariable = Integer variable + level of picked unit