No, a sitting president cannot be arrested for criminal offenses they may have committed while in office. They can only be impeached by Congress and removed from office.
Impeachment
No. If the President runs for a second term of office, he may name a different person as running mate provided the nomination convention approves, but he can not fire an elected vice president. A Vice-President can only be removed from office involuntarily by impeachment in the House of Representatives and conviction by the US Senate.
Treason,
If he is found to not be fit to stay in office, the cabinet can vote to have him removed. Then the vice president will become president. If the president can state in writing that he is fit to continue in office than he may continue. The cabinet then has 48 hours to present a case against the president, to have him removed. The reason that this is in the constitution is for medical reasons. This may not be entirely right, but that is how I understand it. Another way in my opinion would be if the president were to break his oath of office. (Which our president has done several times)
He can be fired by tampering with the instruction given to him to tell others or by harming the president in any form.
The president, vice-president and federal judges can be removed from office for committing crimes. First the person must be officially charged with a crime or crimes, this is called impeachment, and then the person must stand trial in the Senate where a conviction requires a 2/3 vote. Members of Congress, however, are not subject to this process.
The President of the United States has the power to remove officials from office if he sees them as derelict in their duties in some way, but the action must be approved by Congress if the official does not simply resign. Judges on the Supreme Court, members of the Cabinet, the Vice President, and members of Congress cannot be removed by the President but he may ask them to resign.
The only month of the year in which no U.S. President to date has died is May.
On May 28, 1830, the Congress passed the Indian Removal Act. This was under the governance of President Andrew Jackson.
He is impeached or charged by the House and convicted by the Senate.
The President of the Treasury Board serves at the pleasure of the prime minister. The President of the Treasury Board may be removed at any time by the Governor General (on the advice of the prime minister), and is removed whenever the prime minister resigns, dies or is dismissed.