Yes, Oppo K1 has Full HD+ AMOLED on-cell display.
No. Oppo K1 is not a waterproof mobile phone. You should be careful while using it.
Yes, Oppo K1 does have the Corning Gorilla Glass 5 protection.
Yes, Oppo K1 does support dual 4G VoLTE.
Yes, you can record 4K videos on Oppo K1.
Keeping in mind that the Oppo K1 is the only phone with an in-display fingerprint sensor in its price band, the launch price of Rs. 16,990 is not too bad.
At the price, it has great performance, a good battery, impressive cameras and much more. It is also the cheapest smartphone you can get with an in-display fingerprint sensor.