The word prohibited means forbidden; banned. Many people would associate "forbidden" with "no".
For examples:
It depends on what you mean by prohibited, but the general answer is no, not legally.
Prohibited means something that is banned or forbidden, off limits. So 'not prohibited' means that it is available.
Yes, it is a adjective.
yes
Yes, engine brakes are prohibited in this area.
Yes. Banned is another word for prohibited. Outlawed is another word for banned, or to make illegal.
yes
Ever heard of Dictionary.com?
prohibited means not allowed
yes. most of the time visiting was prohibited in POW camps.
Yes, the use of engine brake is prohibited in this area.
Yes, the use of the engine brake is prohibited in this area.