Rinse it out.
You can rinse it with a power washer. You can rent one from Home Depot for 1/2 day. If it is really bad (power washing doesn't remove it all) you could leave a puddle of water in bottom of pool (maybe 50 gallons) add a gallon of muriatic acid, and use a brush on a stick to wash down the pool. This acid is very toxic. Use gloves , rubber boots and goggles and rinse with clean water if you get any on your skin. If you are uncomfortable working with chemicals, you can hire a pool service company to acid wash the pool. They will use a stronger solution, which will remove alkalai buildup as well.
The water can be drained outwith a hose.
Yes, drained above ground pools are not structurally able to handle wind loads. The water helps the pool maintain its' shape.
Fill it back up?
I cant see why it should be drained and given a chlorine bath at all. If there is no problem with the water or the looks of the pool leave it alone.
600 US quarts = 150 US gallons
The pool probably should not have been drained until the ground had a chance to drain. The weight if the water in the pool helps to support the wall againt the groundwater pressure.
Pool brush and occasional chlorine or water changes so it doesn't grow in the first place
Vegetable oil is relatively to get out of a pool that is filled with water. The oil does not mix with water and will stay on the top layer. It can either be scooped out in a cup or the pool can be drained and refilled.
No, You have to have a salt/Chlorine generator or you'll just be swimming in a slime salt water body of water.
However long it takes until you have drained the pool and disinfected everything, filled it back up and tested the water.
Get
There are a number of causes that could lead to tiles popping when a pool is drained. This could just be stress on the tiles.