1. Yes - in fact, it's wrong. 2. No - it's not possible. Try thinking of the word 'start' here as meaning 'trigger' or 'set off/set in motion' - as in start an engine or a fire. This is the secondary meaning of 'start,' and it explains why a) you need a direct object b) 'begin' is not a synonym

1) Yes. In fact, I would go further than unnatural and say it's wrong. It sounds horrible. 2) This is a very interesting question as no, we wouldn't say he began the fight. It sounds very, very strange. 'Start' and 'begin' are actually not synonyms here, 'started' actually means something more like 'instigated (i.e. he was the one who caused us to start fighting. Incidentally in what I just wrote you could say 'begin fighting' as I am referring to the initiation of the act of fighting, not alluding to who caused it.) This is a subtle distinction. If someone 'starts a fight' we are saying they are the instigator of the fight, it's kind of a set phrase I suppose. Edit: What I have just explained is probably why it sounds so bad to omit the 'it'. We are not making reference to the time the fight started, but instead who caused it.

I would say part one is great. That is what we would say in the north of England (It may differ by region as it is not formal language) I would not use began. Logically it works, but it is not something I would ever say.

1) Yes, it is unnatural in this case. But in colloquial British English at least 'he started on me' is completely fine - it means that he acted aggressively towards me. 2) When talking about fighting, 'started' is much more common - began has a strangely formal tone in this context.