There's a flashback that starts at 15:45 on episode 14 of season 1. I've been watching Ranma over the past few days, and I don't think this scene was in a previous episode.
As I recall, the information in the flashback came out as part of a comedy routine. Anime back in those days often had continuity errors like that.
Is this flashback referring to a deleted/modified scene, or is something else going on?
I think you may instead be referencing episode 15, as this episode introduces Shampoo and has a flashback to the Martial Arts Figure Skating battle, which was originally planned to be air before this episode.
Two episodes were cut from the first season, Wikipedia notes the reason as there being a sensitive feeling of the title and theme of the specifically the first of these episodes (The Abduction of P-Chan), due to many kidnappings happening in Japan during that time.
These episodes were later inserted into season 2, which is where the clips come from.
