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.
Puberty starts at different ages for different kids and it is a process that takes a couple years. In general, a major growth spurt occurs at the time of puberty, usually between 11 and 15 years in boys. During puberty, they will have a growth spurt and grow to their adult height. Most boys will have their last growth spurt into their late teens. A few of these boys may grow into their early 20s. Your child should reach his adult weight by this estimation: adding your and his father's heights in either inches or centimeters, then adding 5 inches and dividing by two.