First question, depends on the virus. Some viruses are pretty fragile
while others are quite hardy. I don't know what would happen to the
effectiveness of your tobacco emulsion as a pesticide after boiling.
Second, I assume you're asking if antibiotics will help prevent/cure
virus. The answer is antibiotics are completely ineffective against
virus. The are toxic to various bacteria, not viruses.
Third. Requires expert analysis. You could take guesses as to what virus
it might be, and check to see if you were correct using some sort of
specific test, usually based on an antibody specific to that type of
virus. Otherwise it requires very careful analysis, including electron
microscopy etc to define the virus.