Hello again Mohammad.
Usually, when one uses the term GRE over IPSec, we are usually talking about IPSec tunnel mode. When we are referring to IPSec over GRE, it usually means using IPSec transport mode. But again, there is no clear cut definition in such terminology. For more information about tunnel and transport mode, take a look at this other post in which I responded to one of your posts.
I hope this has been helpful!
Laz