I just ORDed last month. PES E1. I heard uncles saying PES E no reservist. But some say E9 also got reservist. So what leh? Need to do anything? And how many cycles?
If you are assigned/posted a unit after you ORD, chances are you will be called back, whatever your PES status. I don't really remember when I got assigned though.
For me, I was assigned to a unit, but I was downgraded to E with about 3 ICT left, so my unit still called me back even though I was PES E.
In any case, as long as ns.sg reflect your status as PES E, you basically cannot go outfield. You might sit in some office do admin work though.