Can i set up a 7speed gear and disc brake on hercules rocky mtb 2.0 cycle My cycle is a non gear cycle .Can i set up disc brake and 7speed gear.

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In short, no.

There are two main problems:


Your bike does not have disc brake tabs.
Your bike does not have a derailleur hanger.


To be fair, it could be done, it would just be so expensive that you'd be better off buying a completely new bike with gears and disc brakes. If you chose to pursue this project, you would need:


a new fork with disc brake tabs (with the type of fork you have, this might actually be pretty hard to find)
some sort of disc brake conversion kit for the rear (I know that these have been made in the past, but they may be hard to find now. I'm also not sure that I, personally, would trust something as important as braking to a conversion kit.)
A new set of wheels with disc compatible hubs and an internally geared rear hub.
disc brake rotors
disc brake calipers
A gear shifter that's compatible with whatever internally geared hub you decide to buy
a derailleur cable
new brake cables


And I'm sure it goes without saying that you'll need some tools and a good book about bicycle maintenance.

I think that covers it. You're probably looking at $500 (US) minimum, probably more like $1000. 

For that price, just buy a new bike that has discs and gears.