Decks, Patios, Porches and Docks - 22" deck, not attached to house: help!

I'm going to build a deck or raised platform next to the house. I don't plan to attach it to the house because the foundation is granite. Although it will be as close to the house as possible, the only place it will be connected to the house is at the step from the existing landing. Surface height is about 22" above ground. The deck will be roughly 20' x 8'. The width will be ~6.5' in places as it will go around a chimney. Two steps will come down from the deck to the ground. From the frost map, frost line is about 36". I have a couple of questions:

1. Since it is not attached to the house, do I really need to dig concrete piers for this or can I just set the concrete blocks on top of the soil or on top of some concrete pads?

2. Is it necessary to attach it to the house?

3. Does dual beams, about 6' apart and running the length of the deck, and with supports every 6' sound reasonable?

Does not need diagonal bracing as it's less than 24", but does need footings and correct attachments, see pp 9 and 14 here: http://www.awc.org/Publications/DCA/DCA6/DCA6.pdf