Yes. Yes even one try is addicted to some people it alters brain wiring in susceptible population - http://learn.Genetics.Utah.Edu/content/addiction/ follow the link to learn more.
Yes its true! Most addicts will tell you that the first time they used a new substance it was an overwhelming euphoric experiance. Their goal is then to repeat that experiance. No chronic changes to brain may take place yet except to memory of what that first time felt like, and that is very powerful. That does not mean this happens to every person who uses meth, but why play russian roulette to find out.