Cts won't start after oil change

There is none.Idle is controlled by your computer. If you have problems, check these. Vacuum lines behind throttle body. You may have to replace your air flow sensor. You can also try this:
Engine cold.
Turn your key to on position for a full minute. Don't start the car.
Turn key off for 10 seconds
Turn key on for 10 seconds. (Don't start)
Turn key off for 10 seconds. Then start the car. Might work but in all probability your main airflow sensor (MAP) is the problem.

A reset is ten minutes on and 30 seconds off. One time. Relearn is three times this. Older vehicles used to be 5 to 10 seconds off. now is 30. There are minimal times on and off, but I haven't found the maximum time. I have left cars on for 30 minutes and off for 30 minutes and the reset/relearn has still worked. Just a note , the securit relearns in the off position.

Turn key to RUN postion, do not start the engine..
slowly depess gas pedal to floor three tiems within 10 seconds and then turn key to off.

Your vehicle is equipped with an engine oil change
indicator system. The "Oil Change Due" message will
flash in the EVIC display for approximately 10 seconds
after a single chime has sounded to indicate the next
scheduled oil change interval. The engine oil change
indicator system is duty cycle based, which means the
engine oil change interval may fluctuate dependent upon
your personal driving style.

Unless reset, this message will continue to display each
time you cycle the ignition to the ON/RUN position. To
turn off the message temporarily, press and release the
MENU button. To reset the oil change indicator system
(after performing the scheduled maintenance), perform
the following procedure:

1. Without pressing the brake pedal, push the ENGINE
START/STOP button and cycle the ignition to the ON/
RUN position (Do not start the engine.)

2. Fully depress the accelerator pedal, slowly, three times
within 10 seconds.

3. Without pressing the brake pedal, push the ENGINE
START/STOP button once to return the ignition to the
OFF/LOCK position.

NOTE: If the indicator message illuminates when you
start the vehicle, the oil change indicator system did not
reset. If necessary, repeat this procedure.

Source: Owner's Manual page 293

Dodge Charger Owners Manual

change the fuel filter and check the fuel pressure

Done cars have a kill switch if they are low on oil. Check your oil. If the oil is good, it may be the ignition switch.

Your battery needs to be around 12.6 volts to start. Try jumpstarting your vehicle, or purchase a cheap battery charger for around 20$, and let it charge for a couple hours.

You should be able to start, what is the fluid level bring it to the recommended level crank it allow the lifter to solidify and compression will build up

i am not sure what you are asking. if it is what i think then you are heading for trouble.
NEVER, NEVER, NEVER run a engine without oil in it. you will destroy the motor. drain your oil, change the filter then add the amount of oil your owners manual says to . Then start it and check for leaks.

Did you also check the air filter? The Cadillac CTS is very finicky about the differential pressure across the air filter. Checking the air filter often causes the hose between the air filter box and the intake to come loose or start to leak. This will cause the car to run rough or die immediately after starting.