Yearly
Every year
Where ever you purchased your extinguisher from you should be able to return to them to get it refilled. If they do not do refilling they can direct you to the proper place.
It depends upon what type of extinguisher it is. Many refillable types must be internally inspected on one-year intervals. Others only after 3, 5 or 6 years. NFPA 1 13.6.9 prescribes timetables for inspection, maintenance and recharging of portable fire extinguishers, for reference, although it is not universally adopted.
Commercially speaking, in the UK they have to be checked annually, and signed.
Fire extinguisher
Flammable metals often require special chemicals to extinguish, assuming there are any. So, in fact, you WOULD use a "chemical extinguisher", but probably not an ordinary dry chemical extinguisher.
the base of the fire
Fire extinguishers should be inspected annually - by a suitably qualified person.
at the base of the fire
at the base of the fire
Downwind from the fire.
ABC, BC or C. It is often best to disconnect the electrical power and use an extinguisher appropriate for whatever type of fuel happens to be burning (A or B). Do NOT use a water-type A fire extinguisher on an energized electrical fire.