If your baby really doesn't like being on her tummy, leave it for now and try again another time. Bear in mind that babies develop differently, some more quickly than others. If your baby isn't rolling over by the time she is six months or seven months old, talk to your GP or health visitor.
Some men stop growing at 18, some at 21. Some men grow really quickly early on, and slowly grow taller until they have hit somewhere between 18 and 21, while others grow quickly later on and some just grow gradually. So, only time can tell you, no one else can because everyone is different.
Boys often keep growing a little until age 18 or 20, but it depends on the growth plate fusion times as above, which can vary from person to person but usuall go in the same sequence. If you didn't get X-rays then no one knows your bone age. Extremely short kids are sometimes given rprescription medicine to help growth, but this must be started early and is not wise for boys who are in the low low range of normal height.