早上在iMore看到此篇教學文:http://www.imore.com/how-downgrade-ios-91-beta-back-ios-9
發現技巧在某樓提到的:" if you choose "Update" instead of "Restore and Update," it will replace your 9.1 beta OS with the official 9.0 release OS, without deleting any of your user data!
也就是教學文裡 How to downgrade to iOS 9 on your iPhone or iPad 提到的第2點:要選「更新」而不是「回復」
結果真的成功了,照片、紀錄有的沒的都還在,但app要重新安裝,不過安裝完後,紀錄也都還在,像line for ipad。