Purchase bill

Gave my laptop for a service and also purchased an AC adapter from a shop

Purchase bill: I am a student. Last Tuesday (07/01/2020) I gave my laptop for a service and also purchased an AC adapter from a shop in Ritche street. When I asked regarding the bill, he (the shop guy) initially refused to give but when I insist on a bill he gave a delivery challan which contains the laptop adapter (Rs. 650) and power cord (Rs. 50) but no mention of the laptop service for which I paid Rs. 800/-

Difference between the purchase bill and the delivery Challan

My question is regarding the difference between the purchase bill and the delivery challan. Can a delivery challan replace a purchase bill?. Delivery challan contains details of particulars, quantity and amount paid but not on details regarding gst taxes. Can I demand a bill for the laptop service from him? That shop owner seems to not providing a bill for any of the purchases or services in that shop.

12 months warranty

The Ac adapter (not a branded one) that I purchased mentions 12 months warranty on the box but it contains no warranty card and details regarding how to avail the warranty and when I use it, the adapter heats up very quickly for which I want to return the product back. Can I insist on my money back if he could not replace it?. I request your legal advice regarding all the questions.