Hello, i have checked and indeed this is a bug, all unlocks from 2'nd stage are skipped (issue with a bug fix for having multiple copies of same dress).
1. Please create a bug report (check the game description at the end), it will include your save file which i can fix and send back, and send it to my email nymphokyun@gmail.com. And yes, all females have cross dressing system (including hairstyles for Nishy), males only offer cloths, no hair styles.
I'll upload a fixed game version in a few days.
2. Also about the summer event, it unlocks by visiting the dress cabin on the beach area every day after completing the barmen's quest. You must get near barmen then to cabin then back to barmen (until you get a notify about dress cabin), then a new piece of clothing is unlocked. Pony hair style unlocks on 5'th day of unlocks (you must unlock every day, and last one will be hair style).
Apologies for the issues,
~NK