A Memorandum of Understanding (MOU) isn't an aviation term or practice, it's a general business/legal term for a 'pre-contract' of some kind. Before two companies commit to a legally binding and perhaps very expensive contract, they'll often prepare an MOU to make sure that everyone involved has the same understanding of what will be in the contract. That way, there shouldn't be any big surprises or fundamental disagreements when the real contract is prepared.
In the context of aviation, that could be things like how many aircraft will be purchased and when, or what the price is anticipated to be, or anything else that both side consider important. That means that the information in an MOU could be very interesting for other parties ("can you explain why our competitors are paying you $50m less per aircraft than we do?"), so they're usually confidential.
Another common use for MOUs is for PR/Marketing purposes. If two companies are discussing a joint business venture they might come up with an MOU and use it to generate market interest or even raise capital ("I know we're a small company but we have an MOU with Boeing to jointly research alternative fuels").
Given that background, I don't think it's likely that you'll get any specific answers to your questions. An MOU could include all the things you mentioned but only a real contract is enforceable.