Is overkill 3 offline or online?

Overkill 3 does have an offline mode so you can play it on the go without internet. SoulCraft is one of the best RPG games on Android.

Do Sims know they are in a simulation?

The Sims are not self-aware, they are individual computer programs powered by code. They cannot determine on their own if theyre in a simulation or not. The only way they can find out theyre part of a simulation game is by being told so. Sims in The Sims 4 are powered by some form of A.I. thats for sure.