Re: The meaning of omote and ura
I will start out by saying that the way I usually describe "omote" and "ura" is that they describe nage's location or direction relative to uke's center line. So, if nage moves through uke's front center line, it's usually "omote," and if nage moves through uke's rear center line, it's "ura." In this way, I, at least, distinguish "omote" from "irimi" and also "ura" from "tenkan" "irimi" and "tenkan" refer (for me) in a basic manner to the general footwork that nage takes. (So, there can be an ikkyo omote irimi, ikkyo omote tenkan, ikkyo ura irimi, and ikkyo ura tenkan.)
With that said, I'll continue by saying that there are many different approaches to basic movements (kihonwaza) in aikido that says "this foot here" rather than "that foot here." I've seen conflicting ideas about which foot goes where, which hand goes there, and so on from different teachers. So, with that in mind, I'd say that, in the end, I don't think it matters which foot goes first for omote and/or ura -- but, it's certainly important to know what your instructor expects you to know for your kihonwaza training at your dojo...
Just my thoughts,