I have a 91 GMC truck, the passenger side front brake caliper piston is not returning after I press on the brakes, I just replace the dust boot and the square cut seal and cleaned out the caliber,

No you need to change the caliper that is what is locked up on you...

I was hoping to save some money that's why I bought the repair kit and not the whole caliper, I'm going to take the caliper off clean everything out, remove the piston and the seals and lube them with new brake fluid then reinstall it.

yes I've had a couple others tell me it could be the brake line pinching as well, the complete caliper and piston rebuilt is only $22, the brake hose i assume is the original, it's dry but flexible. is there some way for me to test the flexible hose at home?

I replace the driver side and the passenger side hoses, and bought a rebuilt brake caliper for the driver side front, it still having the same issue, do I need to rebuild my brake master cylinder?

okay so I rebuilt the master cylinder, I have to say the brake pedal has never been firmer, feels like it would stop on a dime, but the passenger side front will still not release, when I left the vehicle overnight the caliber seems to retract, but once I press the pedal a couple of times it holds pretty solid can't seem to get the vehicle over 25 or 30 mph