What kind of tachycardia were you told you have?Svt? I know that alcohol can aggravate heart arrhythmias.
That's an individual thing. I can tolerate 1/2 a beer but no more. I can't drink any wine and I don't drink any hard liquor at all, ever. But even a glass of wine will trigger my arrhythmias. Not worth it in my opinion. Other people I know can drink all kinds of fancy drinks without any problem at all.
Not sure where you live but in most places you're not quite the legal age for drinking. I do remember in D.C. beer was allowed at age 18. So be careful.