All the options given are techniques associated with genetic engineering.

Option 1 suggests that genetic changes can be introduced into cells that produce eggs or sperm in prospective parents. This is indeed possible through techniques like CRISPR which can target and modify specific genetic sequences in germ cells — the cells that give rise to eggs or sperm. So, statement 1 is correct.

Option 2 states that a person`s genome can be edited before birth at the early embryonic stage. This is also true and it`s known as germline genome editing. Scientists have successfully used techniques, including CRISPR, to precisely edit genes in human embryos. Hence, statement 2 is also correct.

Option 3 indicates that human induced pluripotent stem cells can be injected into the embryo of a pig. This is a process called `chimera creation,` and it has been achieved in mice and rats. It is theoretically possible to do it in pigs, although it`s ethically controversial. Thus, statement 3 is also correct.

Therefore, option 4 is the correct answer with all three statements being true.