Cisco phone proxy will support on cucm 8.6 or not

Question

Hi as per document i can see that Cisco phone proxy . Without using vpn connect . Customer want to keep configured Cucm on there Jabber or cisco mobile on the iphone and need to get connected when ever they have an internet access .
And also by keeping a small end router at branches havin only one cisco phone needs to connect to the corprate office using proxy.
Is that possible and also is it possible on 8.6 cucm version . Here am just attaching a document info which says version supported
Supported Cisco UCM and IP Phones for the Phone Proxy
Cisco Unified Communications Manager
The following release of the Cisco Unified Communications Manager are supported with the phone proxy:
•Cisco Unified CallManager Version 4.x
•Cisco Unified CallManager Version 5.0
•Cisco Unified CallManager Version 5.1
•Cisco Unified Communications Manager 6.1
•Cisco Unified Communications Manager 7.0

Answer 1

I understand the VPN solution is a good one, but we have already 100 proxy phones deployed and from what I read I'd need to first set up a VPN phone on the cluster before deploying it in the field. This would be difficult to do with users all over the country. Or am I missing something?
I have a question about our ASA though if anyone can answer it. We have to move from an ASA 5510 to a 5520 due to the 100 UC proxy-phone license limitation (even though we have 70 phones it appears that a UC license is taken up for each TFTP server configured on the phone - primary and secondary). When I configured the 5520 I can register new phones no problem. None of the existing phones will register until the CTL file is manually deleted on each phone. Is there a way to seamlessly migrate to the 5520? Such as using the same certs, CTL file etc.. on the 5520? When I configured it it generated it's own self-signed key and CTL file. I did import the certificates from CUCM...