1. I think, that it is a quitar, because it's very beautiful and melodical instrument I have ever heard
2. Maybe, it's panpipe, it's not very popular in our time, because it's known as a folk instrument and it's not very popular for teenagers and adults
3. Fortepiano and grand piano
4. The most important thing to learn playing a musical instrument is to be satisfied with your choise of instrument and like of process of learning