Can you update iPhone using cellular data instead of Wi-Fi?

This works, but is limited to Models that support 5G:

• iPhone SE (3rd generation)
• iPhone 12 mini
• iPhone 12
• iPhone 12 Pro
• iPhone 12 Pro Max
• iPhone 13 mini
• iPhone 13
• iPhone 13 Pro
• iPhone 13 Pro Max

or later, and requires a generous data plan.

Hi, go into Settings, Select Your Profile from the top of the menu, iCloud, iCloud Backup, toggle the switch “Backup Over Mobile Data”.

Even if it works, the update will likely be much faster over WiFi, assuming you have a good signal.