2004 TrailBlazer: seat belt of passenger side can not pull out in tr...

The power seat and the seat heater should be on seperate circuits. The only thing that comes to mind in relation would be the wiring connections under the seat. If the power seat and heat control are on the same switch assembly, I would suspect a switch failure

Some times you can't. However, using a long thin screwdriver and inserting it into the ratchet assembly you may be able to move the ratchet mechanism to release it. Look for any debris or a twist in the belt that may be causing the assembly to jamb

Try under rear seat drivers side. That is where one is on a 2004.

First you reach for the tab near the center of each "half" of the back seat bottom at the back (in the crack of the seat). Pull the tab forward and up, pivoting the bottom of the seat toward the front. Ensure the front seats are forward enough to allow the seat bottom to lie flat on the floor. Next, reach up along the (outer) side of the seat back, and lift the lever, while folding the seat back forward. You may need to pivot or remove the headrest(s). The seat back should lie flush atop the upside down seat bottom. This works for my 2002 Olds Bravada, which is supposed to be similar. Good luck!

The Trailblazer has two fuse panels, one is under the hood on the driver's side above the wheel well, and the second panel is under the rear passenger seat on the driver's side.

Dead Battery

It sounds electrical. I would check your fuses.

You need to replace the driver side temperature door control actuator. While doing this... make sure you bolt the new one in AND THEN PLUG IT IN or it will spin and not line up in the right place... then there is a series of crazy steps to fix that problem.

Yes there are 2 places under dash or sides of dash and in the engine compartment

That is the power distribution center, the fuse box is under the dash to the left of the steering column under a cover, they are marked, the plastic cover will have FUSES molded into it.