I haven't used my car for 2 years. It was outside uncovered. I can see that the brake pads and rotor disc are almost completely covered in rust.
Is it safe to clean the break pads and rotors with brake cleaner and drive after that or I should replace both break pads and rotors?

 

Brake cleaner will not take care of the rust....but you can use it with no problem. You can also just drive the car for a while and make normal stops....it's going to make some noise when braking, but it will go away after a few stops

Bryan

 

More to the point, after two years, your brake fluid should be flushed, especially since it's been outside and not driven.

 

Good advice... most people never flush the brake fluid... you should have seen some of the cars that came into the shop complaining about poor braking.... the fluid in the system was like wheel bearing grease, with the same viscosity

Bryan

 

Your problem is likely to be the handbrake frozen on. The pads rust to the discs. They can be a bear to free if so.Brake cleaner will do nothing for you, save your money.
Try driving it slowly. If all the wheels turn, they will sort themselves out. They will be a bit fierce until the majority of the surface rust is worn off. Start gently. Drive it around some until the brakes feel good before diving into traffic or going fast.
You may well have some stubborn pitting left. If they work ok, don't worry about it, but check your pads a little more often.