Some people with liver disease must eat a special diet. This diet helps the liver function and protects it from working too hard. Proteins normally help the body repair tissue. They also prevent fatty buildup and damage to the liver cells.
Advise is a verb, and advice is a noun. So advice is what is given, while the act of giving advice is called advising (or to advise).
An opinion is different from actual advice. Legal advice is a pretty gray line, frankly. But it generally comes down to something like: this is the law and this is what you should do in your specific situation. Keep in mind though that the specifics are going to be defined by jurisdiction.