It sounds to me like you have a couple of things going on here.
For the rear brake locking up, All I can tell you for sue is to inspect both sides and see if everything is installed correctly and in good working condition and check to make sure that there is no contamination of the braking surfaces. I would need to know if your vehicle is equipped with 4-wheel disc brakes or with front disc and rear drums to give you any specific instructions other than this.
For the front disc brakes going through pads, there are a couple of common causes for this. The first and easiest thing to look for is bad brake hoses. The brake hoses are mde up of several different layers. There is a rubber outer layer and a braided steel layer, followed by another rubber layer and finally, the inner layer, which is usually a silicone-based "lining". The reason I told you all this is so you can understand the "science" behind what I am about to tell you.
Sometimes, the inner layer separates from the other layers inside the hose. It will allow the fluid to be pushed into the caliper from the master cylinder, then when the brake pedal is released, it acts like a "heart valve" and collapses inside the hose, trapping the brake fluid in the caliper, keeping it from returning to the master cylinder. This will keep your brakes applied almost all the time.
Checking for and verifying this condition is very simple. Raise the front wheels and support the vehicle. Remove the front tire assemblies. Start the engine and push ******* the brake pedal, then shut the engine off, release the brake pedal and immediately try to turn the hub and rotor by hand. If it will not turn easilly, open the bleeder screw on the caliper. If fluid squirts out of the caliper and the brake releases, replace your brake hose.
Please note that this condition CANNOT be diagnosed by "looking" at the hose. The hose will most likely look normal when observing it from the outside.
If the hoses are not the problem, then you need to check your caliper guide pins to make sure they slide EASILY in the caliper (please see picture below). Remove the guide pin bolts and remove the caliper from its mount. Then push on the guide pins with your finger. They should slide back and forth with only moderate finger pressure. If they are really hard to push or will not push at all, you basically have 2 choices:
1. you can "wrestle" the things out of the caliper and purchase a caliper guide pin kit and install it in the caliper -OR-
2. You can replace your caliper
The first option is considerably cheaper. However, it is also much harder and more time-consuming to do and will not come with a warranty. The second option will require you to bleed the brake system after replacing the caliper, but most aftermarket parts outlets have options for warranties including lifetime limited warranties from some outlets - you will NEVER have to pay for calipers or caliper guide pins again.