I just downloaded the expansions and it seems like they have two different execs which have the same name and title. Are they really parts 3 and 4 and part 2 or are these simply repeats of the first portions?

Same question.
Opened a ticket but instead of trying to simply download them to see the issue they asked more questions.
To be clear, on the website those dlcs are splitted in parts but the exe and the data are repeated: for 2 parts we get 2 exe, for 4 parts we get exe on part 1 and 3 while data is on 2 and 4. They are not the same files it seems as the size differ. We cannot check md5 or date of the files because instead of implementing this much needed feature they preferred worsening the website usability with a layout made for mobile.

On Galaxy, if you try to download the installers, it fails.