IPhone – How to make itunes stop asking “do you want to allow this computer to access information” on the iphone

Reset the SyncServices folder. Not sure why I didn't think of this earlier.

In short:

/System/Library/Frameworks/SyncServices.framework/Versions/A/Resources/resetsync.pl full

Apple has some other tricks to try if you're on an OS prior to Mountain Lion, but it looks like this should work for Leopard through Mountain Lion.

You can confirm by comparing output of

grep -ir "device" ~/Library/Application\ Support/SyncServices

before and after resetting the SyncServices folder. You should see some lines about your device prior and no lines about it after.

There isn't an easy way to have iTunes show you the last sync data.

You could use Time Machine to compare the files in ~/Music/iTunes after the sync with before it. (Or just restore that entire folder or the entire Mac from a backup before the sync.)

The automatic sync that happens with a new computer is not any actual transfer of files as you would have to go into iTunes and set up the rules or accept the automatic sync of content so unless you already had synced that device to that iTunes library before no data would transfer.