Mukul Gahlot

Whether the thing has a mirror in it is irrelevant. What you need is something that will record in that resolution for the price. I think you are more likely to find mirrorless cameras doing that, since the only DSLR I'm aware that will shoot 4k at 60fps is the 1dxii and that is obviously nowhere near $850. 
 
I mean you will have issues finding something that shoots 4k at 60fps that isn't a camcorder in the first place. I dont even think the gh4 will do that and thats the only camera likely to be anywhere near $850. The gh5s does, but thats it. Honestly, I think the only 2 cameras available that will do that short of cinema cameras are the 1dxii and the gh5s. The a7s line only does 4k at 60 as far as I'm aware and the g7 maxes out at 30 fps as well, which is probably your best bet short of a camcorder. The fuji xt3 will do 4k at 60fps, and is probably the best for it, but is still double what you want to pay for it. 
 
EDIT: Also, there are cases where a camera will do the frame rate, but the lens you have in front of it makes for less sharp results, thus a 1080p capable camera may produce sharper looking footage. 
 

It's more likely that you'd find a mirrorless camera that is able to record in UHD in that price range.

No. You won't find a DSLR that will match a mirrorless camera for videography at the price point you're looking at.
 
Few cameras offer great quality 4K video below $1,000, none of which are DSLRs. You also won't find recording times much past 10 minutes or so on DSLRs even close to $1,000.
 
I highly recommend the Panasonic Lumix G7 and Panasonic Lumix G85, both are excellent cameras for the money, and both offer extended recording times. (30 minutes @ 4K, "unlimited" @ 1080p)

You should't even consider DSLR for your scenario.
There are 2 good DSLR video camera, one is canon 80d the other is 5d Mark 3. both doesn't support 4k.
 
There are another option though, its hybrid prosumer camera like sony RX10 lineup and Panasonic FZ2500.
Both have full fledge videography features but cannot change the lens.

hey yo buddy the discussion has been shifted to the general column (this link) so please follow the same discussion there as there are far more participants there.

The next step up (Lumix G85) only peaks at 4K 30FPS, so not likely from Panasonic. The Sony A6000 which is around the middle of the two in terms of price doesn't even allow for 4K recording, just 1080P 60FPS. The A6300, which is closer to $1,000, can do 4K 30FPS and 1080p 120FPS.

I think it'll be a few years before we get 4K 60FPS in the <$850 price range.

If you're in a studio, with a good lighting, on a tripod, with an external recorder, then it would serve you good.
A good external audio recorder like a Zoom H1 is just another $100.

Ok, now thats a thoughtful suggestion. Thanks.

Thanks bravo i finally looked at dell G5 again and ended up buying it as there was an offer going on for $100 off and made the deal only for $1,099 and you won't believe the specs i have purchased 
8th gen i7 8750H GTX 1060 6GB 16GB RAM 1TB HDD, 128 m.2 SSD Gigabit networking card USB Type C with Thunderbolt If it wasn't have been your recommendation and that offer i wouldn't have bought such an awesome machinery thank you so much.

All with 8750H CPU (must undervolt, repaste highly recommended):
HP Omen 15t dc with 144Hz IPS
Dell G5/G7 - low sRGB FHD IPS
CyberpowerPC Tracer III 15 (TongFang GI5CN5E) - low sRGB IPS ONLY
Lenovo Legion Y530 - low sRGB IPS (144Hz IPS is better but out of budget)
Eluktronics NB50TK1 - desktop CPU (delid recommended), low sRGB IPS