Help with two wierd problems

My blazer has to wierd problem. First when I put me truck in park the rear hatch opens.

Second

When I start my truck put it in gear. I have full power all gear shift well. The moment I let off the gas or press the brake all gears are lost. I can shut off the truck for around 3 to 5 minutes start it up. The tram shifts and has power until I stop or let off gas.

When all gears are lost the motor revs when I press the gas and goes no where