Speeding carries its own set of demerit points. Speeding in designated zones will increase the fine, but wont change the points.
Your charge carries 3 demerit points. As it seems you are aware, any charge with 4 or more demerit points carries an automatic suspension for a novice driver. You are safe on that front.
I'm pretty sure any 4 or more demerit point charge isn't counted towards your overall points total once you've been suspended, but don't take my word for it. If you need a copy of your abstract, you can purchase one immediately online in pdf format and check for yourself. I don't know any of your previous history or whether or not you've accumulated enough points elsewhere to put you into suspension territory.
Any roadside reduction can be brought back up to its original charge if you end up in a trial.
It's also possible you could be offered a reduced charge that would leave you with zero points for this incident.
Points also don't show up on your record until they day you are convicted. If you wish to request a trial, you can put off having the points for several months. On your trial date, you will be offered a deal if your charge has enough flexibility for it. You can continue with your driving tests in the meantime.