The last target of Press into Service can be any creature, even one that’s untapped, one you already control, or one targeted by the support part of the spell.

Gaining control of a creature doesn’t cause you to gain control of any Auras or Equipment attached to it.

As Press into Service resolves, if at least one of its targets is still legal, it will resolve, affecting only targets that are still legal at that time. If none of its targets are still legal at that time, it won’t resolve and none of its effects will happen.

You can’t put more than one +1/+1 counter on any one target using the support action.

Support can target a creature you don’t control.

If a spell with support has other abilities that target creatures, those abilities and the support ability can target the same creature.