Apple organise a Worldwide Developers Conference (WWDC) each year. It’ll be this June. We’ve to purchase the tickets (based on some random selection) on 20th April 2015.
If in case I’ll get my entry ticket, would I get my visa to USA thereafter?
If yes, I would apply for which kind of visa so I can get it without doubt?
Not quite sure what the question is.
You could book a tourist trip to the USA and ask for a visa for that.
If you want to wait till April 20th after you get the ticket you need to check the wait times to get a visa interview appointment and the processing time. I checked for Chennai and it’s a week to appointment and one working day to get a visa. Delhi is only 2 days longer. Aka you have enough time.
Or are you asking whether you will be given the visa just for that? We can’t answer that. Attending a conference is a perfect reason for a B1 visa but whether you have enough ties and funds is something only they will decide.