2. Shelves are not moveable, as there are cooling elements attached to the bottom of the shelves. The shelves have about 9-10" of height, so you can't put a round bucket of chum in there. Flats will go in there, as will 2 and 3 gallon pails of clams, etc. Repackage using rubbermaid boxes (as shown in the pic, and you can get quite a bit stored away.
3. Interior capacity measures out at about 12 cubic feet.
4. Not sure about the age, I've owned it for about 8 years, got it from a neighbor who was moving and had no room in the new place. It could be 20 years old, but I'm honestly not sure. It works great, keeps my ballyhoo at about 5 degrees all summer long and can freeze enough block ice to fill two 100 quart coolers in a week.