Giving an ultimatum, with threat of self harm no less, isn't how you ask for something. Now, I don't know the full situation here, and am not asking for it to be given, but IMHO, demanding something with the threat of self harm is the exact same thing as a 3 year old having a temper tantrum and holding their breath because their parent denied them something they wanted, but didn't necessarily need.

My brother threatened to self harm if he didn't get a cell phone at one point in his youth, and he was a one of those troubled youth that had to be sent away to a camp for troubled youths before he recognized that his behavior would create big problems for him.

As for your second inquiry....Hitting anyone, no matter the situation, isn't acceptable. It's also against the law and considered assault and battery and the offender can be charged and sentenced to jail time, or upon further evaluation, can be sent to a psych ward for treatment as they are hostile towards others, and possibly themselves and require a course of treatment to neutralize that threat of hostility.

So yeah, while I don't know at all what is going on, I can honestly say with 100% certainty that this behavior isn't at all acceptable in anyone, much less a teenager or grown adult.