you can do segmented runs yourself, but that's not really a leaderboard thing. you can speedrun each disk separately, but in order to do a full any% run on the leaderboard, you have to do RTA

Single Segment means that you don't restart the console, turn it off, or lead a save. RTA means that you can do that but everything is timed. Also no idea for the multiple console thing.

I endorse a category for segmented speedrunning. So far I have not seen a complete segmented speedrun of the English version.

A run where you save only at disc change (i.e. saving after each disc to divide it into 4 segments is considered a segmented speedrun and is very valid, but will NOT be comparable with single-segments or RTAs).