Which one is the best for multitasking gaming business and multimedia ..??
Out of those choices definitely the AMD FX-8350. It is superior in Multitasking and Multimedia whilst being more of a tie in Gaming and Business when compared to a 3570K (Gaming due to GPU bottlenecks mostly).
There would be any problem if I overclock the cpu for a long time ??
Depends on the CPU cooler you'll be using (don't use the Stock cooler if you plan on overclocking) and also depends on the motherboard (get a board with a 8+2 VRM Power Phase if you plan on overclocking an FX-8350).
Why Intel processors are priced high than AMD processors.
Because Intel is like Gucci (you pay for the name) and their processors do tend to be faster in heavy computational tasks (mostly in single threaded tasks).