Prohibition and why most federal laws banning things are unconstutional.

In 1920 the 18th Amendment to the Constitution was passed to and prohibition began.

So answer this question!

If congress can regulate anything they want and ban things then why was it necessary to pass the 18th Amendment to ban liquor? And later repeal it to legalise it?

The answer is simple they do not have the power to ban anything unless the constution allows them to do it. True they can regulate the Interstate commerce in products but they can not regulate the "instate commerce".

If congress needed the the 18th Amendment to ban liquor then how do they ban and regulate the instate sales of drugs without a similar admendment allowing them to do so?

How can they regulate instate gun sales?
How can they regulate wages?
How can they regulate any business that is not invlved in Interstate commerce?