Replaster the pool and keep the water chemically balanced (PH, alkalinity level etc..) this will keep the plaster from pitting thus keeping it smooth for a longer life.
Theoreticaly Yes
concrete
No. An older (possibly better) type of Fiberglass pool was constructed in this manner, with a concrete/Gunnite/Marcite trowled bottom and Fiberglass panels at the side of the pool. Panels are caulked together along vertical joints. Actually not a bad deal, but caulked joints must be maintained. Once the concrete starts showing through at the bottom of the pool, its time to drain and resurface. Bottom of pool should be acid washed every 3-5 years to keep it sparkling and remove mold, mildew, stains. If bottom surface is chipping off, its getting close to time to resurface bottom of pool. Bottom is treated just like any concrete/gunite/Marcite pool surface. Sides are simply brushed, caulked in timely manner.
Yes it can be done
What type of surface is it? Concrete, Vinyl or fiberglass? If you have a vinyl or fiberglass pool and it is rough it is probably calcium that has precipitated out of the water you will need to have your pool water analyzed by a professional swimming pool company. If your pool is concrete it could be calcium also or it could be an etching of the concrete both are related to water chemistry and the same professional analysis would need to be performed to resolve the issue.
The experts at Advanced Pool Coatings have been installing fiberglass coatings over vinyl liner pools for over 30 years. You can read more at: http://www.advancedpoolcoatings.com.
It sound as though there is a water balance problem. Take a sample of the water to a pool shop where they will test it and tell you what the problem is. balance the water and the problem will sort itself out.
I think you can as long as the yard is level, the concrete is in good condition and thick enough, and you use sand in the bottom of the pool. Consult your local pool shop for advice.
No, because gunite will not dry if it is constantly being mixed with water. Drain your pool first.
Steel walls are currently the lowest quality wall for a swimming pool, with the exception of Cyprus wood (if still available). Concrete (not gunite) is superior to any other wall, but a pool with concrete walls generally also has a concrete bottom. In other words, it is a concrete swimming pool. The most popular wall today for vinyl liner pools is fiberglass and, with the possible exception of concrete, is the best possible choice.
the concrete should be 6" according to this site http://www.de-fontenay.com/poolcon4.htm
Fiberglass. Over time concrete stains and can become rough, where fiberglass retains its smooth texture. Fiberglass will also give you more options.