Can i change my laptops processor i.e., i wanna upgrade my i3 to an upper level, minez a lenovo g50-70?

Some laptop and portable computer manufacturers allow their customers to upgrade their processor speeds. However, if available seriously consider the upgrade in speed and the cost, often for the amount of money spent and the little increase in performance it may not be worth the upgrade. This upgrade often requires the laptop computer or portable computer manufacturer or authorized repair shop to perform the upgrade and is not something an end-user will be able to do.
If you are curious about the availability of upgrading your laptop or portable computer processor and the cost involved you must contact the laptop manufacturer for additional information.

Though that model comes with 3 available processors, it's not likely that you can change the processor to one of the other ones, as they are all soldered onto the motherboard.

Lenovo G50-70 Laptop | Entry-Level Laptop with DVD | Lenovo US
http://shop.lenovo.com/...tech_specs