Unable to turn on Legacy support and save bios. Displays not working on boot after bios save & exit.

[PulsarLight]

Laptop is Pavilion g6 2301ax,

Comes with AMD a8 4500m with 7640g +7600m graphics integrated

Upgraded to AMD a10 4600m 

Graphics chip is not changed.

Ram: 4gb ddr3 sodimm. Condition: OK

HDD: hitachi 500gb condition: ok checked via memory and hard disk diagonostics via HP bios

.

Laptop was working fine after upgrade for several months, no heating issue at all.

No other hardware upgrade.

A few days ago i started playing Mass Effect 2 game. 

I was working fine for few days.

And last day when i was playing laptop just turned off.

And while restarting again display didn't turned on but rest of thing were working fine. 

No heating , no power issue ,

I did hard reset many times by removing battery and pressing power button from 30-60 seconds. But nothing worked.

Then i found a solution to remove CMOS for few seconds and try.

Now this works and i am able to see display, bios, i can login and use windows. 

But now the ISSUE IS THAT I CAN NOT ENABLE THE LEGACY MODE IN BIOS.

AND MY GRAPHICS DRIVERS ARE NOT WORKING EITHER.

when i try to enable legacy mode and press save and exit. 

Laptop restarts but display not starting like it is disconnected. 

And is if remove CMOS and try again it resets changes back to legacy mode disabled.

How can i fix that? 

I tried older version of bios. (insyde bios) and i tried win+B but no luck.

On other hand with graphics driver. 

If i install via any mode.

1. Amd provided setup

2.windows update method

3.manually updating from Device Manager

After some seconds display flickers and goes black and never gets back to normal. Laptop restarts after several minutes. 

But windows stucks on logo and rotating dots. Dots stops rotating and after several minutes it restarts again and same is case.

I can get to safe mode, disable one graphics out of two (dual graphics) in device manager or uninstall both and i can boot into windows.

Its been three days now. and i have tried reinstalling windows (same version latest) and older version(1803). But no luck.

I was using phoenix OS  along side windows 10 and that stucks at boot too.

I had replaced CMOS with same voltage and numbering too. But nothing working.

Using windows without graphics is of no use for me.

Ram stick is one and i have tried both slots.