I'll give a run down of what I understand the answers to the unaddressed questions are:
1) Before last year when a
treaty was signed, most inter-faction interactions on a military level were at their most friendly passive aggressive and waiting for the other side to give a good reason to allow shots to be fired. Now though there is some small push both in character and out of character to be more friendly to one another with at least
one plot working with a multi-national crew.
2) a) As far as I know promotions are handled differently from GM to GM. Some will provide promotions at the end of a mission, or the beginning of the next, while others might require you to take action IC to earn your promotions and will only provide advancement through the ranks should your character prove they deserve it. So if you're interested in pursuing a rising career through the ranks it is probably best to ask the GM(s) of the plot(s) you join to know for sure how things will go.
b) Funds/pay are another thing... So far as I'm aware they're generally largely ignored IC. I think the general policy is that each character gets a monthly paycheck for every month in real life that you're active in a plot, and at your GMs discretion you can have access to those funds depending on the time frame of the plot (since in general they tend to lag behind real time before time skips happen between missions.) Again it is best to communicate with the GM running the plot as they will have opinions on what resources they want their players to have access to.
3) By 'mimic computer' I'm assuming you're referring to the
mimicom, however I'll answer for artificial intelligences in general... So far as I'm aware the only limits on these sorts of intelligence are those that are put in place by either players or the GM. Some AI are limited to non-volitional natures, however those should have their status noted on the wiki page. As such if it doesn't say it has any restrictions, you can assume that pretty much anything goes so long as a GM doesn't have any complaints. There are however cultural and legal aspects to consider, for example
Yamatai treats any sentient intelligence as a free individual and requires that they be treated no different than any other citizen, meaning that you're likely to have a run in with the law if you try to own a volitional, sapient AI.
4) I... Honestly can't give a good answer to this question. To my knowledge there are no plots that are dedicated to those tasks, however since a plot can take on whatever role is desired by the whim of the GM, it is possible that one of our 21 plots is participating in a task of that sort. Perhaps someone else will have a better answer.