Studies have shown that IQ is likely inherited.
https://www.newscientist.com/article/dn1520-iq-is-inherited-suggests-twin-study/
Yes.
Nope. You can have a high IQ and work at a fast food restaurant. You can't force someone to do something just because they are intelligent, intellegence is potential, that's why I don't like people who brag about having high IQs in place of real-life accomplishments. But you can't do a job that requires a very high level of intellegence if you don't have that intellegence.
Nope, there are a lot of factors at play, environment, genetics, etc.