Quikr.com - Defective damaged mobile send to me

On **/**/**** I have purchased Second hand mobile from Quikr.com Pirce **** Rs .My .Order Number ******** ,Sub order no ****** .Mobile is Redmi * ** GB. Mobile category according to website is Fair condition. On website seller has mentioned fair condition mobile has some dents and visible scratches but mobile phone which I have received is damaged and depressed on back panel.
*) Front side mobile touch screen glass cracked and gap in touch screen on both side of mobile.
*) Mobile Auto brightness function not working properly. yellowish color of mobile screen even with full brightness.
(*)when mobile connected to charger for charging apart from charging indicator light just above located home button is also light up.in original mobile phone this is not happened.

I have forwarded images and unboxing videos of damaged mobile to Quikr.

On */**/**** from Quikr Customer care one of female executive informed me that my order is not eligible for replacement because Quikr people have made decision based on my mobile unboxing video that front screen is damaged by me(Actually not damaged by me) order is not eligible for replacement. She has accepted that back side of mobile is depressed and damaged from seller side and it is eligible for replacement but front screen damaged by me so not eligible for replacement.
Now My question to Quikr are who is responsible following problem in mobile.

(*)Who is responsible for damaged and depressed back panel of mobile? It is not a simple dent. Today female executive from Quikr on telephone conversation with me she has accepted that mobile was damaged from back side and depressed from seller side and she has accepted that Quikr has done mistake in quality check before mobile dispatched to me. This is clearly seen in unboxing videos. This is not according to fair category of mobile as mentioned on your website.
(*)No where mentioned on Quikr website or mobile package as instruction to customer that make unboxing video of mobile as proof of damaged mobile?? Luckily i have made unboxing video and it was clearly seen that mobile was damaged from back side and depressed from seller side (it is not small dent) and Quikr has done mistake in quality check
(*)When Mobile connected for charging apart from charging light indicator light just above located home button is also light up. In original mobile phone this is not happened. This indicate that mobile screen was repaired before dispatched to me that why home button light up.
(*)Auto brightness function not working properly. Gap in Touch Screen on both side.

Now quikr.com is not ready to provide me replacement or refund amount for damaged mobile.