Can sneak past patrollers if that opponent has no detector.
"Sneaking past" means you can ignore patrollers when attacking and attack anything you want. You can also attack the patrollers if you prefer. — Sirlin, 03/14/16
When something with stealth attacks an enemy unit or hero, that enemy unit or hero DOES deal its combat damage back as usual. — Sirlin, 03/14/16
If an opponent has the Tower add-on and their tower has already used its once-per-turn detect on something, then you attack with something that has stealth, the Tower will not deal its damage to your stealth thing. It would if it's once-per-turn detect hadn't been used, but it can only damage things it can see. — Sirlin, 03/14/16