Thanks for your update.
Query 1: "Need to change Calendar Header Background color"
We can use the HeaderBackgroundColor which will be available on MonthViewSettings to change the calendar header background color.
Query2:"Need to apply custom font for calendar header, day header and date"
We have prepared custom sample to show demo on "How to apply custom font for SfCalendar". Please find the sample in below.
Query 3: "Need to align the calendar header and cell dates"
Currently we are facing some issue with align the calendar header. We will update more details on October 31,2016.