Doubts relating H1B consular petition

I am currently working for a company who is willing to file my H1B but i want to fly back to India for my brothers marriage (during end of April’15).

Following are my details:
Current Visa: F1 (Master’s student) and on OPT currently.
Tentative vacation:15-30th April
OPT expire date: 7th June 2015
Reason for travel: Marriage

Degree: STEM

Doubts:

  1. What are my possible options(if at all i want to go) and repercussion associated with it.
  2. If my employer files H1B via consular petition…is it counted under masters quota.
  3. Do i need to apply STEM extension as well?

It would be great if you guys can help me out with this.