Does CU coil need to be cleaned annually on a/c unit?

Actually, yes the coils on the condensor unit should be cleaned at least once a year to remove dust and dirt and pollen and debris that build up in it over time. The condensor coil depends on a free flow of air across it and good contact with that air in order to reject heat. If the air cannot come into good contact with the coil's surfaces, the heat will not be rejected and the operating pressure will be high. The dirtier the coil becomes, the higher the pressure will be. When the compressor must work against a higher pressure it will draw more current and that means higher operating expenses. It also means higher temperatures in the compressor's windings and that will wear out the compressor faster. An annual ac check up should include cleaning the outdoor coil, tightening all of the electrical connections, running the system in the cooling mode and observing all of the operating characteristics such as amp draw, high and low side pressures, superheat reading, subcooling reading, and temperature difference of the air across the coils. A qualified hvac service technician knows how to obtain all of that information and how to determine if they are correct or not. If the unit is maintained well, it can give you many years of good service without any major problems. Allowing it to just operate and not servicing it regularly will lead to problems that can quickly become major issues and quite costly to repair. Hope this helps.

Not typically. Normally the air filter keeps the debris out of the coil and what dirt that does get by gets washed out by the condensate continually running down the coil during the cooling cycle. When filters have been left out for a period of time is when coils have to be cleaned. A visual check can be made to determine if it is needed.

There are copper coils on the evaporator and condensor. Not if you are keeping the air filters clean on a residential unit (evaporator.) But this is one reason to keep changing or cleaning them. On commercial units the filters are sometimes not changed frequently enough and part of routine maintenance is to blow out the evaporator coil and change the filters. But then you are often working on the rooftop of a building and not a basement or attic. You might only want to clean condensor coils under unusual conditions (dust storms or lots of salt air)

Motor lubrication, clean debris from around the condensor unit, observe that pipe insulation is intact make sure that the water flows freely through the evaporator drain line (often white pvc) and if their is an attic drain pan that it is free of debris and that its line is also free of debris and constantly keep air filters clean is enough. You would not want to mess around with it so much that you might cause a leak.

Yes, go through all of it. If using an air compressor to blow out debris make sure there is no water in the tank.