Walls and Ceilings - Some basic drywalling questions

A couple basic questions for the pros .....

I have a few sheets to put up in my basement. I'm orienting them up on a 8 foot high wall. When you prop up the sheet on the studs do you let the 4 foot section rest on the ground then screw it in place or do you like to set it up a bit off the ground ? I assume you place the screws approx every 16 inches ?

Also, is using tape really necessary, or can you just fill it with compound ( what is the purpose of the tape, and what happens if you don't use it ) ?

The rock shouldn't touch the floor, install the top board first pushing it tight with the ceiling. Keeping the bottom board a half inch off the concrete helps to prevent the sheetrock from wicking up any moisture.

If you don't use tape the joints will crack!!!

The questions you asked show a level of knowledge I deem insufficient for getting quality results. But that's ignorance and that can be fixed! Keep hanging out here and get a couple of books on hanging and finishing drywall (big box stores carry these) before you start and I guarantee you'll get better results.