(in the US) the US Congress.
The Cabinet includes the heads of the 15 executive departments --- the Secretaries of Agriculture, Commerce, Defense, Education, Energy, Health and Human Services, Homeland Security, Housing and Urban Development, Interior, Labor, State, Transportation, Treasury, and Veterans Affairs, as well as the Attorney General. Their job is to manage their department and keep the President informed about concerns connected to their department. They also give the president advice when asked for input.
Democrat and Republican
The Vice President is President of the Senate and has the power to break a tie on votes in the Senate. The Vice President is also the successor to the Presidency if the President cannot continue serving in office. Vice Presidents have become more involved and more powerful in recent years. They serve as close advisers to the president and often bolster the presidents credentials because of their previous experience in government.
Answer 1: The Prime Minister is the actual head of the executive, takes most of the key decisions and can (usually) rely on a majority in Parliament. The Queen is essentially a figure head.
Answer 2: No. The Queen can dismiss her Prime Minister with a single command and replace him or her with a person of her own choice. The Prime Minister has no such reciprocal power. This clearly puts the ultimate power in the hands of the monarch. The Prime Minister can essentially be regarded as the manager of the Queens's estate, whereas the Queen is the Head of State. The Queen has other powers that the Prime Minister does not have, such as single handedly being able to declare war on other countries, where the Prime Minister needs Parliamentary, and often UN approval.
Answer 3: According to the Constitution, all public power (executive, legislative and judicial) is created and commanded by the Queen. The Prime Minister is, in theory, a counsellor who advises her. In practice, it is a more complex situation, because the UK is a democracy, so public will must be law. So, more or less, the Prime Minister and the Cabinet take the executive decisions, but it is the Queen, through the Privy Council, who makes those decisions effective. She is not forced to accept all ministerial decisions, this is why she meets the Prime Minister once a week to discuss matters of State and advise him. This is the reason why the Executive is called Her Majesty's Government, to indicate it is her who governs and has the power, not the ministers. Nowadays the UK is a strong democracy, so the Queen will only interfere when the Government behave improperly.
Now, taking into the account the prime minister is appointed by the Queen and the Queen is also the head of Parliament and Courts, she has more authority than the PM.