1. Are announcement posts editable later, as information changes? By this I mean the first post in a thread? If so, why do people "reserve" the second and sometimes third posts of the same thread?
Yes, all posts in any thread (including the first post) are editable, except in the Auctions section (for obvious reasons). People reserve the second and sometimes third post in a thread because posts have a character cap, which probably won't be hit unless you have a very large thread, or to be able to have a nice divider between different information (ie bounties, or latest news)
2. I am about to announce a project that has a fundraising element (you could think of it as an ICO though it's actually a charity, "Initial Donor Offering", not an investment offering). We also need to announce a request for members to join our team as staff/contractors. Would the best way to do this be via two threads, i.e. one under "altcoin announcements" (the one with the donation campaign), and a second thread under "project management" (where we are recruiting a several different competencies to join our team)? I don't want to run afoul of the rules.
Yes, put two threads. One in Altcoin Announcements, which is your actual ANN, and one in either Services or Bounties (Altcoins) as the Project Development section isn't really for altcoins, but rather Bitcoin related projects. Those sections I listed are the ones people look at for a "job".