I drink socially, does this mean I am addicted to alcohol?

No. It's often difficult for people to tell when they're crossing the line into dependency. Generally, you are crossing the line if you: use alcohol to help you get through painful situations or feelings; ever defend or hide your drinking; can't remember what happened after drinking a little too much, resent other people's advice who want you to drink less; drink alone, have problems when no alcohol.
Depends. Depends what you mean by "socially." safe amounts of alcohol are less than 2 standard drinks daily in men, 1 daily in women and people over 60. No amount is safe when driving or operating machinery etc. Men drinking 5 or more drinks on an occasion, and women drinking 4 or more drinks are at high risk of alcohol problems. More important than how you drink is if alcohol causes harm in your life.