Here is the full list of all 11 Frogsong achievements.
Complete Chapter 1
Complete Chapter 2
Complete Chapter 3
Complete Chapter 4
Complete Chapter 5
Complete Chapter 6
Get 100% completion on a save file
Collect all 8 lilystones
Upgrade your blade for the first time at Rimbal's shop
Upgrade your blade further at Rimbal's shop
Perfect your blade at Rimbal's shop