If I use the free temporary storage to transfer my data from an old phone to a new one, will all my data on the old phone get erased once the temporary storage expires? What about on the new one? Is there an alternative to safely transfer data without worrying about this?
iPhone X, iOS 15
Temporary iCloud space to enable a transfer of data to a new device is explained in Apple's support document Get temporary iCloud storage when you buy a new iPhone or iPad - Apple Support
In this document Apple says that you get this additional space for up to 21 days (ie. three weeks). This space is used to store a backup of your old device. This backup is used to "restore" the data to your new device. Instructions for this are given in the linked document.
The data on your old device is not affected and it remains your task to deal with it. Apple provides the steps you might take in What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support.
Temporary iCloud space to enable a transfer of data to a new device is explained in Apple's support document Get temporary iCloud storage when you buy a new iPhone or iPad - Apple Support
In this document Apple says that you get this additional space for up to 21 days (ie. three weeks). This space is used to store a backup of your old device. This backup is used to "restore" the data to your new device. Instructions for this are given in the linked document.
The data on your old device is not affected and it remains your task to deal with it. Apple provides the steps you might take in What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support.
Free iCloud storage for backup stransfer - Will data get erased?
