Hi Mike,
(1) In how long time do I have to take the essay exam after I have submitted my performance based exam?
As far as I know there is no time limit. But the sooner you take the exam, the better so your full design is still fresh in your mind.
(2)Can I take the Essay exam before the performance exam?
No.
(3) If one failed the Essay exam, can he/she retake it?
There is no failing the essay exam per se. The purpose of the essay is exam is for you to demonstrate that you have intimate knowledge of the application you submitted. As long as you are familiar with your application, there is no problem.
They will ask you questions about how you implemented this or how you handled that. Just describe how you did "this" and "that" and all will be well.
Hope this helps,
Michael Morris
Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction. - Ernst F. Schumacher