Not if you're going by boat. If flying, normally yes.
Yes, everyone needs a passport to enter the United Kingdom.
yes
To enter the United Kingdom, you will need a passport and, from many countries, a visa. Once you are in the United Kingdom, you can go to London freely: there are no internal checkpoints.
Yes, they definitely need a passport to legally enter the United States.
yes just like everywhere else
You should check this with the American Embassy. If someone on this site gives you an incorrect answer, you could have a big problem.
Depends on where you are from. But most passport holders (With the exception of European Union countries) need to get a visa before entering Britain.
You can enter the US without it only if you have other proof of your citizenship and identity. If not, you need your passport.
No, you cannot leave the United States without a passport. A passport is required for international travel to enter and exit other countries.
British subjects do not need a passport to enter Ireland if they are arriving directly from the United Kingdom, but you may need your passport for your airline, travel company etc and should check beforehand
Yes. However you will be asked how long you intend to stay etc. and you will need to have a current passport while in Australia unless you have other arrangements with the department if immigration.
Yes, you need a valid passport to leave the United States and enter most other countries.