Data base -> Status - > Make a new skill
Name it what ever you want
new or replacing one
Restriction should be set to => can't move
I made my rating 10
hit % = 0%
and recovery conditions to 1 turn 100%, 0% for physical recovery.
Next
Make skill or item I'll use item
Name it what ever you wish
scope = one enimey
status changed + the status you just made
This should do the trick no script is required.
What ends up happening is that your item causes the status change, which makes them unable to move, (unable to do their turns), since it is over after 1 turn 100% it only lasts for that one turn. IF I am not mistaken 10 rating means it always hit but I could be wrong.
AS for the backwards part I am not sure what you mean since the game makes turns into rounds unless your using a custom battle script, but usually it will go form fastest speed to slowest.