Left knob is night charge, it will take a bit of trial and error over a few days to find the best position, too low and you'll run out of heat by the end of the day. Set it and leave it alone, during colder weather it will need to be set higher.
2,3 correct, when the fan switch is on, the fan will run when the room thermostat calls for heat. 4 is electric heating during the day, this should be left off normally and only switched on to boost the heat if the stored heat has run out, as it is likely connected to the expensive daytime rate electric supply. I would expect the 2 wall switches that share the same plate will both need to be left on for the heating to work, switch them both off when no heating is required during the summer time.
This is an educated guess working from memory but should be correct!