need some input on PCM interchangeability please

[fst100]

greetings, i have a 2010 HHR SS auto and after various tests and diagnosis i am leaning towards the pcm is bad and needs replaced. the car sat for a couple months during the winter and i had some unsuccessful jumpstarts. once it was able to start i noticed after several minutes the car will drop idle and struggle really bad. along with that fuel pressure drops, no response from the gas pedal, and voltage drops to under 12v, AFR goes from 14.7 and stays at 18, and no (pending) DTC codes. few forum members suggested throttle body which i replaced and the issue was still there. i cleaned the MAF sensor and replaced with new MAF and symptoms were still there. i also reflashed back to stock and it didnt work. here's where it gets odd:
if i use either my hptuners or torque app to just clear any codes (remember there are no visible or pending codes), the car will idle normal and i can apply throttle again.
my mechanic friend unplugged the MAF sensor and the car idles fine and gas pedal can be used but AFR is still pegged at 18
with MAF plugged back in but B1S1 AFR/O2 sensor unplugged, car idles normal, throttle is normal but AFR pegged at 18 and according to the scan the mV is always at 0.

i searched on the forums and social media regarding pcm compatibility but did not get anything concrete. i was told i would need a pcm from hhr and 2010 specifically as it has different software than 2008-2009. if that's the case can i get this pcm found here: https://www.amazon.com/ACDelco-12623.../dp/B00559BY6A
if so, can i do a full write with my current tune or will i need to take the new pcm to a dealership or shop that has a tech2 to download a factory file then i can overwrite the file to mine? or will i need to purchase 2 credits to unlock the file and transfer my tune changes to the new pcm?

[cobaltssoverbooster]

so if the mV of the sensor is at 0...did you confirm the sensor is not failed and the signal is in fact being returned to the ecu?
Seems to me like you have more testing to do before you slap an ecu at it.

[fst100]

Turned out it was the o2/afr sensor that was bad but found it odd it didn't give a dtc code

[cobaltssoverbooster]

i've killed a few that did that. I filled one with soot doing rich condition deceleration tuning. Glad its not an ecu.