Board Thread:Love Live! School Idol Festival Lounge/@comment-28184119-20160729105931/@comment-11148831-20160810095359

The above message just tells you that it is possible to transfer accounts using Game Center or Google+. (Only if you're transferring from the same OS though)

Turns out they have to know one more thing before they could try to retrieve your account.

◆今までに当アプリで使用したことがある端末の機種名、OSのバージョンを全て教えてください 機種名（iPhone4、Xperia Zなど）： OS（iOS7、Android4.1など）： This asks for the model names and OS of all the devices you may have used for this account so far. For example: 機種名：ASUS Zenfone 2, Samsung Galaxy S6, iPhone 6S OS：Android 5.0, Android 6.0.1, iOS 9