Ok. Finally I tested it and it worked, but I have another problem that I will explain below...
Step 1.
1. Edited contact - removed phone with international format and left the same number in local format.
2. Checked - it worked!
3. Edited contact again - just edded the same number but with international format ( I need both variations of the same number).
4. Reboot
5. First thing I noticed, that "Personal Ringtone" is not show me the contact name, I see only number.
6. Checket - it worked!
It was at night, now in the morning I checked again setting of "Personal Ringtone" and surprise - it show me also the contact name
For now all is ok... Thanks!

Step 2.
In your description you say "Sounds and Ambience settings will have no effect.", but here I have a problem...
I tried call to myself from another number that not in the setting of "Personal Ringtone" and it play rington that mentioned in "Default ringtone". This ringtone was when I installed "Personal Ringtone". I tried to change ambience with another ringtones a few times, but it still ringing the same rington that was when I installed your app. I changing ambiences 4 times in the day, but default ringtone not chenged in "Personal Ringtone". Why ?
I tried to change it manually, but it see only my custom audio files from sdcard (all my files here), and can't see ambiences audio files.
Why it not changed automatically with ambience, like you say "Sounds and Ambience settings will have no effect." ?
Thanks