of course it's true, young women should wait until they are at least 18 to be sure they are physically capable, and they should have a gynecology exam before they intend to have sex.
Depends on how old you are. If it's too small to fit, then you shouldnt' be having sex. The female body isn't really "physically" ready to engage in sex until 18+, i think even 18 is too young.
well it is possible , and this is going to sound strange too
but as you do it more, your vagina actually slightly enlarges because of being stretched slightly.