The Switch Behind The Pull Cord is for the handle heater as this is the "H" version with heated handles. It has a alternator made into the underside of the flywheel that makes electrical current. There are heating elements in both handles.
Cleaning up an old saw - Blow it off with compressed air first. I sometimes use a stick to get the stuff loose from the the inside corners but never anything metal as it will scratch the paint.
Then use a cleaner like "409", "Fantastic", "Simple Green", or sometimes "Mean Green", and an old clean rag to more or less wash the saw.
The marks and scratches are worked on with a little rubbing compound.
The "i" version Dolmars have a Tillotson carb with no choke. When you turn the so called choke leaver on, it opens a direct fuel path from the fuel pump to the venturi of the carb. The fuel exits through a small orifice close to a #60.
The saw will most likely start and run with the choke on but will eventually quit if you don't turn the choke off. The 6000 and 6800 have a twist on choke lever.