With the iOS update, the process of syncing Puzzle & Dragons Game Data to the iCloud has been changed. Syncing this data allows for account information between iOS Devices to be restored.
Backup & Restore using iCloud
By signing in to iCloud beforehand, Game Data will automatically backup. From the Settings, navigate to the iCloud and toggle the iCloud Drive option to "On".

Under the iCloud Drive menu, toggle P&D to the active position.

When P&D is installed in a new device, it will sync your Game Data to the new installation. This process must also be authorized in the new version.

In the case that the same iCloud account is used on multiple devices, Game Data of the device last played will be restored.
Take caution, shared iCloud accounts also run the risk of corrupting data.
For more information on iCloud Backups, please contact Apple Support. Please perform backups at your own discretion. This method of transfer is compatible between iOS devices only.
For Data Transfer between different operating systems, please see here: http://tinyurl.com/mu8dx4v
For Data Transfers for Android™ devices, please see here: http://tinyurl.com/nyenyvv
*When transferring Game Data using a Device Change Code, selecting “No” at the iCloud Game Data recovery screen will take you to the Name Entry Screen.
*New data transferred from the Device Change overwrites game data that was previously backed up in iCloud.
*This function can only be used by devices with iOS 10.0 or higher.