hello there, When i open hacker news then in my account there is written(1) beside my username. What does it mean actually? And also how could i be able to understand if Ycombinator ask me any query regarding my application.

The number is the count of your "karma" score (acquired points). You can view the score of anyone by clicking on their user name and viewing their profile.

As for questions from YC, they asked you to make sure your email address is set correctly in your profile so if they need to contact you or any of your co-founders, they can. You can set your email address by clicking your user name link.

Actually they ask to keep loggin in HN because they will use this Platform to ask questions regarding the application, right?

yes that's what I remember them saying somewhere too, except I don't know where exactly the message will show up...

yeah this is not clear where that message will be shown in the Hacker news...and how cud we understand that the particular query has been asked to whom??