Dell XPS 15 9550 is absolute unusable after BIOS update

Hi, guys. I'm using the laptop primarily on Linux and have recently decided to update BIOS from 1.9.0 up to latest 1.11.2 from F12 menu.

However, after the update was completed the laptop became absolutely unusable. Everything is freezing and sound plays with a long delay.

The first thing which I tried: Downgrade the BIOS, but the 1.9.0 and this ends with "ME Firmware EndUpdate Failed Error: 0x00002236" and "Update failed". I reset BIOS settings and restored BIOS from BIOS Recovery menu but this didn't help at all and still get this after a downgrade.

Then I tried several distros: Ubuntu 16.04, Ubuntu 18.04, Fedora 30, Fedora 31 Beta, Arch Linux. In every distro I tried various of kernels, nvidia drivers versions(from nouveau to upstream drivers), desktop environments (GNOME, Budgie, KDE), tiling windows managers(i3wm, awesome, xmonad), any possible recommendations from SO (from adding boot kernel parameters to disabling Spectre patch) and still, NOTHING helps at all. The entire system freezes as f....It can't even play 360p video on YouTube (tried in Chrome, Chromium, Firefox, Opera). Also, I have noticed that laptop freezes less if unplug the charger.

Last thing I tried is installing Windows: I wiped the SSD, BIOS CMOS, clean up EFI partition(just for sure :D), and installed the latest Windows version. The latest drivers for all devices were installed but this didn't help. The performance is much better than in Linux but video and UI still freeze in all browsers and windows. For eg: if lauch 4k 60fps video on the YouTube this more like 4k slideshow with a buzzing sound.

Also, I tested the laptop with AIDA64, Dell ePSA, Dell Support Assist and all test are passed. This is pretty confusing for me! I am deeply disappointed by the fact that in such a short period of time the laptop turned into a pumpkin. His inability to work under Linux make a very negative effect on my work and makes me sad.

Please, help me to restore its former performance. I really like this laptop and I'm not ready to change it, taking into account the fact that a week ago it worked perfectly.