Write a query to display the name(s) of the user who has/have answered most number of queries, sorted by name.

This is not easy - or at least, not easy to do if you don't want to group and count everything twice!
Assuming you have two tables (which would be the sensible way to do it)

Users   : Id, Name, OtherInfo
Queries : Id, UserId, OtherInfoAboutTheQuery

Then you can do it using a CTE and a couple of joins:

WITH AggData (UserId, UserCount)
AS (SELECT UserId, COUNT(UserId) as UserCount FROM Queries GROUP BY UserId) 
SELECT UserID, name FROM Users u
JOIN AggData ag ON u.Id = ag.UserID
JOIN (SELECT MAX(UserCount) As MaxCount From AggData) mx ON mx.MaxCount = ag.UserCount