Additional here is the ONLY solution that i have found after hours on end of research, to at least get my contacts back on the iPhone to at least use it for phoning and WhatsApp again:
1. First you need to do the clean update, or if you have left with the last state after the annoying iOS9.02 update after the "cant sync message in iTunes" just stay at the after-install-screen on the iPhone/ipad-screen which gives you the opportunity to "use iPhone with new system".
Click on that option, enter all the nessesary data to make the phone usable (enter Apple-ID, choose language, adjust date and time etc.).
Next go to enter your wanted eMail-Adress-account entering all nessesary data to make it usable. Check if you can receive any eMails on the phone with it.
So once your iPhone/iPad is now rendered with a new usable system iOS9.02 and you are on the mainscreen with all functions of the phone working you may prepare for the rest.
2. Second now, go to your mailprogram (Mail, Entourage or Outlook) and export the contacts of your adressbook as a VCARD-file. Remember the location.
3. Next go to your Mailprogram set up a new eMail to yourself entering the eMail-Adress which is set up on your iPhone. The send the eMail to yourself (if possible with a second eMail account) attaching the VCARD-file prepared and exported before.
4. Go to your iPhone and receive your eMails. Open the eMAil with the attached VCARD-file, click on it.
5. It wil ask you if you want to "create new users from the VCARD-file", click YES.
It will take a minute or so (depending on the amount of contained adresses of your adressbook) and voila! after that minute you at least have back all your needed adresses to use your iPhone again as a PHONE or WhatsApp communication tool.
Sure this is just a little workaround, not giving you back full control over photos, sounds and music under your control. To do this you will have to buy expensive thirdparty-software like e.g. WonderShare´s "Dr. Fone for iOS", "TunesGo Retro" or else.
But at least you could use your phone again, having back adresses.
Hope this helps some other users who are stuck with the similar sync-problem on 10.6.8 and iTunes 11.4, at least as log until Apple is (hopefully) releasing another working iOS-Update (9.1 maybe?) which makes our phones working again the way it should. Also on old machines.
C´mon Apple do something about it...