Flipkart — Return is not accepted

Address:	Kolkata, West Bengal, 700065
Website:	www.flipkart.com/hp-15-ac152tx-p6l87pa-acj-intel-core-i5-6th-gen-8-gb-1-tb-hdd-free-dos-2-gb-graphic

I have bought this from flipkart and order number is-od[protected]
It has operating system as dos. I tried to install windows 8. But it gave very poor performance. The function keys did not work. Audio quality was also very poor.
I called the executives and they raised a complain. After 5 days, i got call from tech team. They informed that windows 8 does not support.
But in specification no where it is mentioned. When i asked them why it is not mentioned, they taught me how to purchase a laptop from flipkart.
The procedure is, one has to select a laptop from flipkart.com. Then he/she has to visit the authorised site of the product and has to cross check its specification
With flipkart and there he/she may get the information what it does not support.
But i guess this procedure to buy a laptop is not mentioned anywhere in flipkart.com. They also told me that one has to buy the laptop only seeing the image
In flipkart.com. After purchse, if one does not satisfy with it performace, or audio quality or video quality or anything else, flipkart won't replace or refund it.
During buying, the image in flipkart is the only way to judge the look and performace as well. Althogth it was mentioned 30days rplacement gurantee.
But to avail this, i have to get the defective certification from the product manufacturer (For me its hp).
They again suggested me to try someother os like windows 7 or windows 10. I tried with windows 7. But the installation does not work.
As many i am trying to inatall, it redirects to the boot manager after the installation completion. Its showing an error message that "tfght" is missing.
I tried with another win7 dvd. But the problem persists. I called them again and raised a complain.
A tech guy call me again and explicitly told that its an os related issue. They can do nothing. If i want to replace, i have to get a written from hp engineer that it is defective.
Else they can do nothing. I have paid 43k. I am trying to get the laptop ready for 10 days. I have invested my money and timebut they did not show any respect.
Could you please guide me what to do?