Apple ID ****

So my lovely but untechie partner has a new to him iPhone 10. Should a piece of cake to upgrade from his 5c to the new lovely shiny one. These are the current problems...

5c won’t download ios10.3.3 and is currently running something like iOS 7 consequently he can’t get the code to verify his Apple ID on the new iPhone 10"

i have tried signing him in on my iPad to get the code but again it needs to send a code to a device that’s running 10.3.3 etc

so an alternative would be to create a new Apple ID which would mean he looses all his photos, general life. He can’t update the password process either anywhere because the Apple ID is based on an email address which he no longer has access to as it’s with BT who have closed his email address when he changed broadband providers several years ago.

how do we achieve the impossible and get him on a functioning up to date phone that will save all his passwords and use his finger print meaning every item he wants to go into something he doesn’t completely loose his mind as well as forgetting the passwords. His iPad is running 9.3.5 and will not update further as it is also ancient in Apple years. If we create a new I’d is there a means of moving all the data from one cloud account to another.

Please send advice, a teenager or hair dye to cover the greys endured by this conundrum!