Yes. The freezer temperature increases by about 20 degrees during the defrost cycle. This is normal and doesn't affect the quality of the food in your freezer. 

 Clean the inside with a mild cleaning detergent. 

For freestanding refrigerators you should leave 5 cm on top and 10 cm behind the appliance. This will allow heat to be dispatched easily and reduces energy consumption. For built-in appliances the space needed is included in the specifications.