Here you go...
Hmm... that looks okay (although you don't need that text in the note field, the alert will display the event title).
So when that alert goes off are you getting this style of alert? Then without clicking anything it goes away?

Here you go...
I don't know this ting is working erratically I just now set one another calendar event and it did not anything on the set time ??
There is a setting in Calendar preference to tell it how you want default events configured. Maybe take a look at that.
I suggest you also take a look at Growl for this kind of thing.
Correct.
Ok, strangely what is happening is when I set an event and then click on alert and select custom in it and then select Message with Sound and when I close it, there are 2 problems even after selecting the time, the Calendar either does not give me an alert on the set time and it pop us up a reminder always saying 2 minutes for a new event whereas the event has already passed and also there is no message with a sound when I have selected one. What happens is, it again goes back to the default setting when I try to choose the custom alert in the alert tab. Attached is the screenshot. What should I do ?