As the nation's central bank, the Federal Reserve derives its authority from the U.S. Congress. It is considered an independent central bank because its decisions do not have to be ratified by the President or anyone else in the executive or legislative branch of government, it does not receive funding appropriated by Congress, and the terms of the members of the Board of Governors span multiple presidential and congressional terms. However, the Federal Reserve is subject to oversight by Congress, which periodically reviews its activities and can alter its responsibilities by statute. Also, the Federal Reserve must work within the framework of the overall objectives of economic and financial policy established by the government. Therefore, the Federal Reserve can be more accurately described as "independent within the government."
Yes, but statute != Constitution.
Cheers!