Likely, but not guaranteed. The interface spec guarantees that calls between two canisters don’t get reordered, but this holds only for every pair of canisters. Given the current implementation I would say you can expect messages to not get reordered (especially if all canisters are on the same subnet). But please don’t bank on it too much.
At the moment there is a lot happening in terms of the new messaging model. Once that is implemented, then I could see some message reordering happen if a canister is under load.
Regarding your concrete questions 1 and 2 the answer to both is No.