Can i burn an Arduino sketch .hex directly using USBASP?
Sure you can - but you don't even need to remove the chip from the Uno.

The 6 pin header at the end of the board (used for SPI) is also the ISP header for the main chip. Just plug your USBASP into there (you can get adaptors for it for $0.99 off eBay) and program it direct.

I think there's even an option in the IDE's menu to select the USBASP as the programmer (or there used to be on earlier versions).