Mac stuck on grey progress bar after Catalina Supplemental Update

Hello all,

I have a Macbook Pro mid-2012 and it is stuck on the grey progress bar every time I try to switch it on. It was working fine till today morning, it was sleeping and was charging but then when I tried to wake it up, it made the startup vibration, showed me a blue screen with a few rectangles. Worked fine for some time, got very slow, and then I went for a restart but it won't boot on. I had updated to Catalina sometime back and supplemental update just this friday.

Here are the things I have tried:

• SMC/PRAM reset
• Pressing Shift Key to go into Safe mode, it still won't start up all the way
• Trying to go to recovery mode using Command R, earlier it went, but was stuck at something like examining volumes, now it would not go into recovery
• Tried Option Shift Command R to install OS which came with it originally, nothing happened.
• Tried verbose mode, stopped at pci pause: sdxi... probably some hardware issue; earlier also when I had faced this, I erased disk, installed original MacOS and then worked up my way to MacOS Mojave; worked fine for a few days but since pages and other things were not available, had to update to Catalina and till then it was fine
• Tried removing the unsupported kext files using some command line commands but it had not worked earlier when I had faced the same problem

I had to do this earlier also because I thought it is a problem with my Mac, maybe it is; But I think it is because of the Catalina Supplemental Update (and I feel stupid to have forgotten that because of this tiny update I would have to go through this world of pain), so **** buggy. Request someone to help me out with this please, I feel I am really out of options now ;(

Been stuck at the image below for like 20-30 minutes