Jotrum03 Said:
"iCloud backup from old phone to new: If I log into my iCloud on my new I phone without backing up my old device, then back up my iCloud on old phone can I re-sync my new phone to have the data my old phone had once it is backed up?"
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Successfully Re-Transferring to a New iPhone:
When transferring, this is the Quick Start is the best router to date: Use Quick Start to Transfer Data to a New iPhone or iPad - Apple Support. So, reset your new iPhone to factory settings, and then perform Quick Start transfer.