Generally it takes 4 to 7 days to build a pool but, depending on the weather, the scope of work ie; hardscaping, gardens pool house fencing it could take 2-5 weeks to complete.
The liner is the last thing to be done on any project. It can be installed once all construction is completed and the city/town does their inspection.
Typically pool companies will start build in March or April and in most year can build right up until the first weeks of December.
With vinyl pools you can customize your pool to any size you like, as long as you follow city/town bylaws and setbacks.