Details needed about MP3 play

Wondering if anyone can shed light on the system of file structure for using a USB flash drive to play albums.

I'm finding that, on selecting an album from the file browser, the tracks seem to come up in alphabetical order instead of the actual play order that was saved to the disc.

I have all files actually numbered at the beginning of each title, such as ....  01_TrackOne ... or    02_TrackTwo

but can't find a way to select play order anywhere in the settings or menu. 

In my previous car (Kia Picanto) I had the same issue but there were settings that could be changed to revise the play order. 

The other associated issue I'm finding is that, for each track (or album) I have artwork saved in the MP3 tag but only SOME of these are showing on the screen.

Does anyone know if there is a specified required file type/size that will display naturally?

Again, nothing to find in the settings or online manual.

This is all for the Swing version of head unit.

Thanks.