Yes. Yes - depends on body response - my personal opinion it is the physical withdrawal people fear and eventually stay addicted probably this was the tipping of the scale due to chronic health issues and acidic body type.
Yes, you can ... It is very easy to become physically and psychologically dependent on heroin. The chemicals that are most likely to cause addiction are those that reach the brain quickly, greatly stimulate the "pleasure center", and then leave relatively quickly. I recommend that you visit http://www.abam.net/find-a-doctor/ to find an addictionologist who can help you.
No. No single exposure to any dependency-producing chemical can cause addiction. However, the sensation produces such strong euphoria that there is a strong drive to do it again. It is repeated use, becoming more frequent and using larger amounts of opioids that produces physical dependency plus the social/emotional/spiritual problems that come with it that constitute addiction.