How to merge two Apple accounts by migration

Question

Hello to you all
My question relates about merging two apple accounts.
Having two accounts is an issue (for instance when you start setting up Family sharing, or trying to get phone calls on your Mac)
As we know, merging two accounts is alas (still ?) not possible.
But it should be possible to address the issue it my migrating data.
As many people, I have two accounts:
Account A: [email protected], with all my purchases (iTunes, apps, machines)
Account B: [email protected], with my calendar, contacts, bookmarks, photos...
The best possible option seems to keep account A:
- Transfer the data from B to A
- Possibly transferring the [email protected] address into A
- Close B
About the data transfer:
- Transferring iCloud documents is easy (using the Finder)
- Transferring contacts, events bookmarks is also easy as they can be exported (ex .VCF or html)
- Transferring Notes can be done by moving the notes from the iCloud list to the On my Mac List
- Transferring Passwords and Photostreams is difficult (No Export solution for KeyChains, No way to transfer ownership of a photo stream)
- I do not know yet about transferring the iCloud email address [email protected] into the [email protected]
So my questions are:
1) Do you have any idea about transferring Passwords in KeyChain from one iCloud account to another ?
2) Do you have any idea about transferring ownership of a photo stream to one iCloud account to another ?
3) Do you have any idea about the email address transfer
4) Do you have any other way to do this ?
Thanks for your attention
Kind regards

Answer 1

The easiest thing to do would be to use an iOS device, such as your iPhone to migrate the data from one account to the other.  You can go to Settings>iCloud on your phone, sign out of account B, choose Keep on My iPhone and provide your password when prompted, then sign back in using ID A to create a new iCloud account and choose Merge when prompted to upload the data.  This will not migrate notes, which as you said, can be dragged and dropped between accounts on your Mac. 
This will also not move your existing iCloud email account.  You cannot move an iCloud email account to a new iCloud account.  You would either have to switch to the new @icloud.com email account that goes with your new iCloud account, or continue to use the existing email account as a "secondary account"  To do this, you would go to Settings>Mail,Contacts,Calendars>Add Account>iCloud on your iOS devices (and System Preferences>Internet Accounts>iCloud on your Mac), sign back into account B and turn on Mail.  Just be aware that, at least on an iOS device, this would not be push email as push is only supported in the primary iCloud account.
Photo stream cannot be moved between accounts either, not can it be enabled in a secondary account.  If you want to keep your photo stream photos you'll have to either save them to your device, or add them to a shared album before signing out of the existing account (see http://help.apple.com/icloud/#/mmc0cd7e99).  Another option would be to import them to your iPhoto events, then add them back to your new photo stream using iPhoto when you sign into the new iCloud account on your Mac.
For iCloud keychain, I believe you can turn it off iCloud keychain and you will be given an option to keep a copy of any saved passwords and credit card information on your device.  Then set up iCloud keychain again once you are signed into your new iCloud account.