As promised Sheena,sowhat wrote:Questions... mmm. Let's try.
1. Any particular recommendation on age? What age is the best to start? What are the chances for those who start at, say, 30 (don't worry, i don't want to start a career in music, i'm too old, ugly and talentless for that)? Are there any differences in starting recommendations for teenagers and mature people?
With the exception of babies and very small toddlers, age should never be considered a detrimental factor to learning any new musical skill. Learning to play an instrument well has same basic requirements for people of virtually all ages. For example if we focus on learning to play guitar the only mental or physical limiting factors that may have to be overcome in some way are the inability to comprehend or remember structure and form of the music the individual wishes to play, or a severe physical impairment of the hands. As we know some physical impairments have actually enhanced the ability to play music, I am of course thinking of people like Stevie Wonder and our very own (Canadian musician) Jeff Healey who have little or no sight, but are world renowned musicians.
As far as the best age to start, I can only draw on my own musical experience when answering that question so that will have to suffice until others take an opportunity to share their thoughts on the subject. My father could not play a note on anything and neither could my mother. Never the less I was exposed at a very tender age to a broad spectrum of music. The music of Tommy Dorsey, Mario Lanza, Frank Sinatra and Slim Whitman* could often be heard in our household. My father loved Sundays. He would put Radio Luxembourg on the radio and turn it up to 11.
IIRC I started playing a penny whistle around age 3 at the behest of my grandmother. By the age of 5, I was noodling on the reed organ that she kept in the parlor. I played flute in school at a very young age. I took music theory at school until I was 16. The tune Red River Rock was the turning point for me. I wanted to play guitar so badly after hearing that record. Buddy Holly later became my idol. By the age of 14 with the aid of my father I owned a Hofner Les Paul copy and a Vox AC30 amp. A short few months later I was playing in my first blues band - The Confederates.
*Slim btw had to teach himself to play guitar left handed because he partially lost a finger on his left hand.
Starting late in life may only be as limiting as your time is limited to devote yourself to becoming a good musician. Chances are that if you start at a young age and you want to pursue a professional career badly enough, then you will. Those chances tend to decrease as you get past your mid twenties and the pressures of making a living and having relationships take away your focus on your music.
I hope that with the personal anecdotes and examples that I have given you, that I may have in fact given you some hope, because where there is hope, opportunity usually exists as a silent companion.
Answers to your other questions to follow.