Depending on how you look at it, either one (ethanol) or all (all forms of ethanol... gin, vodka, whiskey, brandy, etc... with a few specific exceptions for beverages with very low alcohol concentration or intended solely for medicinal or religious use).
Prohibition was the largest social conflict in the 1920s.
alcohol
Generally speaking these are called temperance movements. Teetotallers encourage and practice absolute abstinence from alcohol, which is not necessarily the case for all temperance movements. Prohibition in historical terms was the legislation of teetotalism, though prohibition can obviously apply to many other kinds of behaviors that don't even necessarily involve use of intoxicating substances.
blood alcohol
There have been several kinds of prohibitions throughout history. Anything that isn't allowed is 'prohibited' and it can be said there is a 'prohibition' against that item or behavior.
There are three types of alcohols, ethyl alcohol, propyl alcohol and methyl alcohol. Ethyl alcohol is the type that is consumed.
No. It is the quantity of alcohol that raises the BAC.
There is only one kind of alcohol in alcoholic drinks. That is ethyl alcohol.
Fernet-Branca, Firewater, Frangelico
The great majority of liquid cosmetics - perfumes of all kinds for instance, are very largely alcohol.
There are dozens of different kinds of alcohol. It is probably safe to assume that enough of any of them would kill you, since too much of just about anything can be fatal, including water. The three most common kinds, ethyl alcohol (beverage alcohol), isopropyl alcohol (rubbing alcohol) and methyl alcohol ("wood" alcohol) will definitely kill you in sufficient quantity. In fact, the last two will do it even quicker than beverage alcohol, and with methyl you get to go blind, too.
In common terminology the term alcohol refers to ethanol. However, in chemistry ethanol is only one of many kinds of alcohol. Only ethanol (a.k.a. ethyl alcohol) is used in beverages.