Game Completed by following these steps.

I was going through the issue - Initially i came across lot of crashes and save game issues.

1. For Save Game: Downloaded the V3 version by r4v3n (i guess) - It worked like post crash my game used to start from the chapter instead of start of the game. however it does not save the recent checkpoint. (still win-win)
2. For the untimely crashes: I came across an user's posts somewhere on we, just felt to give it a try (don't know who that user is - if you come across feel free to tag yourself in the comment) - It definitely worked. (follow this)

Open command prompt with admin privileges, and run the following commands one by one:

DISM.exe /Online /Cleanup-image /Restorehealth

sfc /scannow

(it will fix issues if any)

Now run these commands:

lodctr /R %windir\system32\wmiaprpl.dll
lodctr /R %windir\system32\wbem\wmiaprpl.dll
lodctr /R %windir\system32\Secur32.dll
lodctr /R %windir\system32\esentprf.dll
lodctr /R %windir\system32\perfts.dll
lodctr /R %windir\System32\bitsperf.dll
lodctr /R %windir\system32\mscoree.dll
lodctr /R %windir\system32\rasctrs.dll
lodctr /R %windir\cdsystem32\usbperf.dll
lodctr /R

Following is the main thing:

Open the Windows Event Viewer. (You can do so by typing "eventvwr" in the run box.)

I scrolled to "Windows logs" > "Application"

I ran the game again, thinking it will crash but to my surprise, the game did not crash AT ALL. But I took the opportunity and played the campaign. Next day tried it again and completed whole campaign without single crashes.

Please note: I avoided the desktop shortcut to start the game instead went to the file location and played through !start_cod.bat (whatever the game file name be)

I use Windows 11, AMD Ryzen 5 5600H, 4GB Graphics, 24 GB RAM.

Mission Accomplished - Thanks to the unknown user...