I HAVE A 2001 AZTEK AND WHEN ON AN UPHILL INCLINE STOPPED, YOU MUST KEEP FOOT ON BRAKE OR VEHICLE WILL ROLL BACKWARDS

Better to do that with a high end scan tool. You can't do it by disconnecting the battery overnight, but that can cause all sort of new problems. Where you say your speedometer 'sets' at 55mph, do you mean always stays at 55 even stopped, or do you mean if 'sits' at 55 even if you are doing 110?

The most likely cause of all this the VSS (vehicle speed sensor)

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This is when you need to let the clutch out just enough to stop the backwards roll when you take your foot off the brake, then you can move to the gas pedal and when pressing the gas pedal you can release the clutch all the way to get moving. IT is a matter of practice and timing..

this is normal as there is clearance built into the parking pawl in the transmission to make it easier to go from park to a gear. I`m guessing this happens when you put the car in park on a slight incline. if you walk up to any car and push against it when its in park it will roll slightly until the clearance is taken up in the parking pawl, this is the clearance that you have.

manual transmission clutches wear, making it necessary to adjust clutch pedal position, much like brake pads wear. Check your vehicle clutch adjustment by finding out if clutch pull point, or friction point is approximately I/2 the distance from all the way pressed to the floor and all the way released. does not need to be exactly halfway, but should be close. If the clutch release point is up towards the top vehicle clutch definitely will not hold completely, and allow vehicle pulsing roll. This will indicate clutch adjustment, or even require replacement.

I agree with Enrique.
Just to add, Maybe you can take shift linkage loose and move tranny lever by hand, see if you can get it into park position? There are safety issues trying to do that, You don't want the vehicle to move. Safety is your responsibility. If the vehicle is on an incline, you may need to nudge it a little, so the tranny isn't holding the vehicle.
Can you check for applicable tranny codes, if there are any?
Just because the dash lites come on, doesn't mean the battery has a full charge. Just my opinion.

You should always use your parking brake. Leave your foot on the brake,then apply the parking brake. If you don't,the only thing holding the car, is the mechanical parking pawl in the transmission,and yes, it could break or fail to hold the weight off the vehicle,and it would roll away,as well as damage the trans.

Yep, tranny problem

There is a little gizmo called the BTSI (brake trans-axle shift interlock) that is usually the culprit for this problem. It is located sorta under and towards front of shifter.

t sounds like it could be two or three things:

1) Your park shift interlock isn't working. I think you are on the right track mentioning you had your foot on the brake. Usually, when one steps on the brake with the car in park, the interlock solenoid (BTSI) will "click" as it releases. Do you hear the solenoid? Perhaps the brake switch isn't working or is mis-aligned. It is up under the dash near the pedal hinge point. Do your brake lights come on? If so, the solenoid should be getting the signal it needs.

2) Another way the problem can occur is if you park on an incline and do not set your parking brake before you shift the transmission into park. Failure to set the parking brake first allows the weight of the car to roll against the "parking pawl" in the transmission. The weight of the car would bind things up. Going to have to rock the car up the hill to relieve the strain, something that would take another person if the incline was steep. In your case, you'd have to leave your foot off the brake to move the car to relieve the strain, then put your foot on the brake to engage the interlock.

Good luck, keep me posted

There is a bypass for the safety switch, unfortunately you have to remove the shift cover, the whole plastic piece. there is a white "lever" that you can push that will move the pin out of the way so you can shift it, you have to hold the piece and move the shifter at the same time. it is on the right side of the shifter base (under the plastic piece) you will see what I mean when you remove the center piece.
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Assuming this is a standard transmission, you always have it in 1st gear. Roll back is controlled by balancing the clutch with the gas pedal.

If an automatic transmission, then the vehicle should hold itself on the incline, unless it is a steep incline, to which you may use the gas pedal to hold the vehicle on the slope, and not the brake. And you would always have the transmission in the main drive gear position.

It means you must have your foot on the brake pedal in order to shift gears.