I am going out of country for 3 months is it okay if i leave the bike unused for 3 months ? and what to do to protect my bike for any loss ?
Disconnecting the battery is a good idea, specially if you have an alarm on it, to avoid it being discharged.
Besides that I'd leave the gas tank full (or close to full) so the water condensation inside the tank is minimal. Also, check the bike's manual to see the engine oil expiration (mine is 4000km or 6 months, whichever comes first) so you know if you'll have expired oil once you're back.
3 months is probably enough time for the engine head oil to be drained to the crankcase, leaving the cylinder unlubricated. So before the first start you might have to add some lubricant oil through the spark plug hole and start the engine without it for a while, so the cylinder walls get lubricated. This last step could be avoided if you had someone to start the engine at least once a month.
 Though it's what the manual says, I never met someone who waited that long to replace the oil, some go as far as changing it with 1000km. I try to stay in the middle ground and change it with 2000km checking the level and apparent quality of the oil (viscosity and color).
 As @Solar Mike pointed out in the comments, the oil expiration based on time is actually at the very least debatable. This question talks further on the matter, pointing reasons why this kind of recommendation does not have technical motivation. I'm still leaving it in the answer as it's recommended on some proprietary manuals, but adding the observation that you can choose not to follow it incontestably.
If it's carbureted I'd drain the float bowl.
Mix a few ounces of transmission fluid into the fuel, then run the engine until you get the oily fuel burning. Shut it off & either drain the fuel now - or later when you return. Fuel goes bad in as soon as 60 days. The transmission fluid will remain in the carbs & keep things open after the gasoline evaporates. Sta-Bil brand sells engine fogger spray for longer term storage. Their fuel stabilizers work somewhat - I prefer to have fresh fuel, so my stuff runs better.
Fuel: mix in some Sta-bil (or similar fluid) in with the fuel, and top off the tank.
Oil: TIME DOES NOT HURT OIL. If you let motor oil sit in an engine for 10 years, it will not change. Things which damage oil are: usage (aka mileage), heat, dirt, water. If you are getting relatively close to an oil change, I would recommend just going ahead and changing it real quick. You will have nice an clean oil when you get back.
Chrome: spray all metal surfaces with ACF50, WD40, or a similar anti-corrosion spray. (Before you start the bike in 3 months, remember to wipe these surfaces down.)
Storage: cover your bike with a (blue) plastic tarp.
Battery: the battery will probably be fine sitting for 3 months. You might need to jump it the first time you try to start it again. Any longer than 3 months, and I would suggest taking the battery out and hooking it up to a battery tender.
Safety: purchase either a disk-brake lock, or a bicycle u-lock. This will keep thieves away.
Leather: if you have a nice leather seat, and the weather is going to be extreme (hot or cold), I would suggest storing the seat inside.