03 cts i put it in park on a hill and let go of the brake then it started to click and slowly roll back

Is it parked or while driving. If driving go get the brakes looked at. If parked then my guess is it's a manual trany and the engine compression is not so good. First if parking down a hill put the car or truck in reverse and point the wheels towards the curb so when it rolls 10 inches it will stop when it hits the curb. And use the brake also. Again if it's not working get it repaired.

Set the parking brake first, then put it in park, when you kill it. That way the parking brake is holding it, not the tranny. See if it makes any difference? Also, check proper voltage and ground for the starter motor.

Sounds like tcc is still engaged in transmition.

it sounds like your shift lever is loose and now your Park/Neutral safety switch is out of position. Try, with foot on brake, holding key in start while you move shift lever slowly from park to low.

Can't shift out of park because I've parked on a slight hill and my car has backed up slightly jaming the parking pawl in the automatic transmission after I have shifted into park but before I have set the parking brake. This is a complaint that Ford owners have had for years. Try this proceedure to see if this solves you problem and best of all it's Free. 1st when you park develop the habit of; while still having the foot brake down apply the park brake firmly first and then shift into park and then release the foot brake. Remember it is important to apply park brake with enough force to prevent the vehicle from rolling. What happens is in the rear of an automatic transmission there is a coarse gear that has a lever that engages this larger gear and when you shift into park range this lever goes into one of the spaces in the larger gear and stops the car from rolling. If the car starts to roll it can Jam the lever against the gear and make it difficult to shift out of park. By using the procedure I've outlined it prevents the lever OR Pawl from being jambed into the larger park gear. Try to make this a habit and you shouldn't have anymore problems.

Do you park on a hill, and not use the parking brake?? When folks don't use the parking brake, the car rolls a bit after you put it in park, and take your foot off the brake. Therefore putting pressure on the transmission to keep the car in place. Then when you start up, and throw it in reverse, it will pop, clunk, make an awful sound.

This is normal, depending on the depth of the hill. This is frequent with standard/manual cars on uphills, they can roll back, but with automatic vehicles they usually have a small amount of throttle, (you'll notice this when putting your vehicle from park into drive with your foot off the break, it'll start slowly moving forward)
Now on the hill, if it's a steep incline your car will move backwards, it all depends on how high your throttle (the car itself) is, and the incline depth of the hill.

Adjustment will usually help, but try parking with front pointing down hill next time.(back in, apply E brake .) Emergency brakes usually hold better/well when vehicle front heading down hill. If it doesn't hold with front pointing down, then rear brakes need attention.

Is the park brake adjusted properly? u should start to feel resistance on the 3rd click of the brake ratchet, if u don't it need adjustment.

No, it is not normal. Most people use only one foot when driving, no matter the conditions. However, in this situation I think you may be able to recover this issue by keeping your left foot on the brake, put the car in gear, LIGHTLY apply the gas then slowly remove your foot from the brake. However, I would strongly recommend that you take your vehicle to a shop that can service your transmission and see what they say. It could be just a simple adjustment.