You can extend at any immigration office where your address is registered by way of TM30, but keep in mind many offices will put your application "under consideration" for about 15 days, and you MUST return to the same office to have the additional 45 days added to the extension
Draw it yourself. It can be very basic. I once produced a printed Google map showing the coordinates with my condo building clearly marked and was told "need to draw". That's how it is! (That was at CW)
The Work Permit associated with the Visa has to be cancelled first. The applicant then attends the immigration office to request volunteer visa cancellation and request the covid extension