When doing shnayim mikra, may one read an entire parsha/aliyah once, then do the targum, then read the pesukim again? Or does it have to be in the order of its name - first shnayim mikra and then echad targum? Similarly, may one read the pesukim out of order (assume b'dieved - he got confused as to what day it was and read chamishi on Wednesday, for example - does he have to do chamishi again after going back and doing revi'i)? Thanks.
To answer part of your question:
Or does it have to be in the order of its name - first shnayim mikra and then echad targum?
The Birur Halacha (Beginning of 285) writes that reading the entire parsha once and then each pasuk followed by it’s Targum, or reading each pasuk once followed by it’s Targum and then the entire parsha once are both valid options that are halachically the same as the Arizal’s method because the entire issue is reading the Targum close to the pasuk. This is brought by Bikkurei Chaim 3:1 (source: footnote #18 here)
I couldn't find an answer for your specific case, but we see from the bold text above, that not necessarily does it have to be first shnayim mikra and then echod targum. (This doesn't necessarily answer the rest of your question though.)
Rav Eliezer Melamed says as follows (Peninei Halacha Hilchot Shabbos 5:10):
Be-di’avad, the order is not critical. If one reads the verse, then targum, and then repeats the verse – he fulfills his obligation (Levush; AHS 285:3). Similarly if he reads the parsha out of order from end to beginning, he fulfills his obligation. The main objective is to read all the verses twice and the translation once.
Therefore, however one reads it, they fulfill their obligation, even if "out of order".