- is there anything like "stealth" in this game? Is there a possibility of not being noticed even if in enemy's "vision cone", by having cover/concealment, while spotting them themselves? What about hearing movement?
- are potential obstacles partially obscuring the target affecting the chance to hit?
- is there a "moving target" penalty, like in the ol' Jagged Alliance 2, when the target moved significantly their last turn?

There is no stealth. Your soldiers can hear nearby enemy movement and the enemy are alerted by sound of gun fire. In the next version you can attach silencers to guns.

Yes, any object in the way of a target will make it harder to hit. However, the trajectory of the shot is based on precise geometry calculation. Jagged Alliance is a 2D game, so shot hit chance is based on rolling a dice.

No, there is no "moving target" penalty