Gunite pools & custom spas.

Effectively yes, and that is the main reason people choose gunite over the alternatives. The shell is sprayed on site over a steel frame rather than dropped in as a pre-made piece, so freeform curves, geometric lines, vanishing edges, beach entries, tanning ledges, swim-outs and integrated spas are all buildable. The limits are your yard, your budget and the engineer's plan, not a catalogue of moulds.

Deep enough for a diving well if that is what you want, which is something fibreglass and vinyl usually cannot offer. The depth on any specific pool is set by the design, the soil, and local code and permitting, so it is decided on your plan rather than by a standard number.

Yes. An attached spa is shot as part of the same structure, which is why it can share a wall with the pool and sit at a raised level with a spillway. Standalone spas are also gunite work. Either way it is formed and shot with the shell rather than added afterwards.

Three things, and all of them happen before anyone sees the finished pool: enough steel placed to the engineer's plan for the soil it sits in, a continuous pour with the right water at the nozzle so the concrete reaches its design strength, and a proper cure rather than letting the shell dry out. None of those are visible once the plaster goes on, which is exactly why they matter.