Solder, for whatever reason, does not default to sorting by reverse creation date. It sorts them in a way I've not bothered to run down but is definitely out of order. My DatPackRedux is an example: http://api.technicpack.net/modpack/datpackredux . The current build is 5.25.10 and the builds were created in the order you would expect (i.e. 5.25.9 previously, then 5.25.8, etc.). The order returned by Solder is quite wonky.
As for the multi-select, I'm referring to a "multi" select box where you are able to see multiple options at the same time. Would be very useful since you could have the second field auto-switch to whatever you select on the first, then since multiple options are displayed the one you want to compare to should be right below (or close) to the selected version.