Deferring Admission to reapply for some PhD programs next year This question is related to one of my previous questions:

Changing University in First year of Phd

I just completed my senior year. I have been accepted to a grad school (say University X).

I want to reapply for some PhD programs next year (fall). But, at the same time, I don't want to lose the only PhD seat I've got. 

So, I was thinking about deferring the admission to University X in order to apply to few other universities for next fall.

I have 2 questions regarding this:


Should I mention about my deferred admission to Uni X in the Phd applications for next fall ? If I don't, Would it be treated as academic cheating ?
How much deferring should be enough ? (Next Spring, Next Summer or Next Fall)
Deferring admission is not an automatic privilege at most universities at the doctoral level. You will typically need to justify why you want the deferral, and explain what you would do with the time. For instance, a Fulbright fellowship or a "service payback" on a fellowship might be valid justifications to a deferral; applying to other grad schools most certainly is not. If you are found to be deferring at one school to apply to another, you may lose out on admission to both, as the first school may retract their offer, and the second would likely not want to accept someone who might try and hold out on them.