Going on:
2 - IMPERATIVO NEGATIVO - it is formed exactly the same as in "presente do subjuntivo" (conditional sentence), just add "não" (=don't). Presente do subjuntivo: (que) eu viva, tu vivas, ele (a) viva,, nós vivamos, vós vivais, eles (as) vivam. Negative form of the imperative: there is no first person (eu) never! ; não vivas (tu), não viva (ele/ela), não vivamos (nós), não vivais (vós), não vivam (eles/elas).
Obs.: In Brazil, we don't use in oral language the pronoun "vós". It is too erudite.And "tu" is used in some regions. Remember that oral, colloquial language is more flexible. In my state people say the pronoun "tu" joining the verb in the form of the third person (ele/ela), e.g. viva (tu) bem!, instead of vive (tu) bem! You know, spoken language doesn't follow the right grammatical rules many times. And the rules for the verb "vivER" are different from other verbs ending in "ar" or "ir", as cantAR and partIR... that's why people get so confused. So, don't concern too much about it, the most important is to be able to communicate.
If you still have any doubts, I can try to make myself clearer. Bye-bye!