Upgrade questions and obtaining old version of FreePBX

I am running a old version of FreePBX (6.12.65-19) and would like to upgrade to 6.12.65-30. I want to do this because I would like to switch to iSymphony 4.1.10, and the module admin says its not compatible with my current version of FPBX. I no longer have the image for 6.12.65-19, and the website only goes back as far as 6.12.65-29. I would like to obtain that, so I can test upgrading from that point.

Also, I see that if you take a backup using the utility in the admin menu, and then upgrade a point version (lets say from -19 to -20). Then restore the backup taken at -19, it does not restore that point version. I understand this is on a system level, and the only way I can think of doing a true backup is doing a data dump of the disk.

Do you have any other suggestion, notes, scripts on taking a more complete backup?
what is the lowest FPBX version compatible with iSymphony 4.1.10?
is it possible to obtain the iso for 6.12.65-19?
what kind of downtime/availability issues can I expect when upgrading?

Is doing a dd backup nessary? would this even work on a HA system?