There are many factors to be considered. If the home is very nicely insulated and the existing ducting(if any) is in great condition, house is 10 years or younger, no vaulted ceilings, 4 ton is fine, if not, 5 ton is more sufficient.
A qualified contractor should be sought.
600 square feet.
Yes, a 4.5 ton air conditioner would be the minimum size for 2000 square feet.
NO
yes
yes
Yes
1500 sq ft.
300 square feet, or about 15 x 20 feet.
around 400 SF, not ft
The size of the area that a portable air conditioner will keep cool varies depending upon the number of BTU's the unit has. For example, a 12000 BTU air conditioner will cool an area between about 500-600 square feet while a 8000 BTU air conditioner will cool an area of approximately 300-350 square feet.
400 sqft per ton. So no.
One ton of air conditioning can cool approximately 600 square feet of area, if the climate is not too hot and humid. Using that formula, a four-ton air conditioner can cool about 1600 square feet of area.