Hi, congratulations to joining SQ, and welcome to SFC.
First of all, the training that you'll get after OBS will be quite intensive and stressful (at times). Apart from the exams and ATPLs, you'll also be assessed on your flying ability on the C152.
Suffice to say, there will be some cadets who do not pass this phase. Anyway, the attrition rate is approximately 15%, which again, is an average.
Most cadets have difficulty with (not in priority) at the Seletar flying phase, then clearing solo in Jandakot, and finally, the Baron phase just before getting the CPL/IR.
As for Brisbane, it is quite rare to be terminated there, but yes, it is still possible. In fact, we can get terminated (or grounded) at any time, as this is the only profession that you get tested on your competency periodically. So... just have to get used to it.
Anyway, dun worry about it too much, just put your 100% into it. Think about it, there are a lot of other people out there wanting to be in your position, so make the most out of it.
Good luck!