If it's 4x8 x 1/2 inch there are 100 in a 'lift'. If the sheets are 5/8 there can be 60 or 80 to a lift. - The manufacturers try to arrange lifts so that building yards fork trucks can easily and safely handle them. A 4x8 x1/2 lift of 100 is approximately 2.5 tons.
About 94 sheets if 4x8.
Between the sheets of drywall can be insulation or just hollow.
You will need at least 14 sheets, depending on shape and height of wall.
4' x 12' = 48 sq ft
You need roughly 94 sheets, however, the shapes of walls and stairs will change that figure slightly.
Each sheet covers 48 square feet. Divide 1500 by 48 gives you 31.25 sheets of drywall.
3.5 sheets to cover that.
Impossible to say without knowing how many rooms and what size they are.
Drywall is too heavy and large to put on pallets unless you're using smaller length drywall sheets less than 5 feet, which is unheard of unless they're scraps of construction trash or leftover wall board. Drywall in wholesale amounts are delivered by special heavy duty crane/boom trucks that take specialized skilled delivery for upstairs, handcarrying, and are used with special drywall carts that carry 14-17 separate sheets of drywall. Drywall usually come in "bundles" of 2 sheets per bundle. "Bundles" are held together with a pull strip cardboard type tab. Due to the brittleness and heavy weight of drywall, it's very easy to crack or break drywall in half by accident. bundles of weight, thickness, length, and width vary by type of drywall and purpose. I only know because I delivered all the drywall by a boom/crane truck, dolley, and bare hands. JB
That will take 27 sheets.
Depending on doors and windows that is approximately 500 sq.ft or 16 standard boards.
A 'lift' (100 ) of standard drywall sheets weighs about 2.5 tons on a dry day, -so you figure it out according to size of your truck.