Levers

If unit switches lever then gate opens. How to do that?

simple:
event:
destructible - (your lever) dies
action:
destrcutible - open (your gate)

But You need to add another trigger to kill the switch when a unit enters to a region that is around the switch

NO u just use the unit to kill the lever ... same way like in the tft campaign ... its distructible ...

Test your ideas in game before posting

You want to flame me? I DID use levers a million times so i know exactly what i am talking about. it works!