A non-UK subject can indeed be knighted by HM the Queen, however the person knighted will not normally be referred to as Sir. (EG Bob Geldof). Also a person who is being knighted should check that by receiving the knighthood they are not breaking laws of their own country.
No, it would be considered a marriage abroad.
He is not a citizen of the US; however, he is a citizen of the UK and an honorary citizen of Italy.
You should look up "How to become a citizen in the UK". It should be the same.
no
You can easily become a UK citizen if your spouse or civil partner is a British citizen.
To become a UK citizen, one must meet the knowledge of English and life in the UK requirements. They also must be of sound mind, health, and be at least 18.
you either be born in the UK OR passport done in the UK it depends
A US citizen would have to apply for a visa and become resident. Alternatively they could marry a UK citizen. In addition a British Company could invite the US citizen to work in the UK and apply for a work visa on their behalf. There are quite a few ways to do it legally.
Yes, you can.
If the mother and child (the stepchild) are domiciled outside the UK then no.
By proving that they have been in the UK continually for 14 years.-Rajiv
You must be living in the UK and have a right to work there. As a non-UK citizen, this will mean you will have to have a visa that allows you to work in the country or you must already be a citizen of an EEA country.