One thing I was looking at was splits. On the rules it says that you split on the first frame of fade after pressing continue once the level was beaten. Is this true? Also, at one point, I saw my co-0p partner create a custom character called HiBuddyHiAl (y I don't know) with the traits of wonder women. Is this allowed?

Split times (except starting and ending) is by each runners preference. The rules say it is advised, however no mod will hold you to that and deny a run solely for that purpose.

In terms of custom characters, I would say no in Any% and 100% unless they are made there during the run, but for freeplay% or any NG+ categories I would allow them. This would be down for discussion however since there are no defined rules for it.

K thanks