Answers
Tragic Prince:
Getting accepting into SIA to train as a cadet pilot does not gurantee you that you'll get your CPL/IR, frozen ATPL and type rating on a widebody.
You still have to go through the training program, and if you can be trained to fly a plane, then you have increased your chances. There are losses in each training course, usually in the beginning stages, up to Jandakot, where clearing your first solo is the first main hurdle. Having said that, there are also Second Officers who were terminated by SIA. So, there is absolutely no gurantee that you will be a pilot when you get accepted.
The usual attrition rate is approximately 10-15% for each course, however, it can vary from course to course, so this is just an average.
SLK:
From your qualifications, yes, it seems that your paper certs are not recognised by SIA. If you have A levels, then your 'allowance' is S$500. Diploma holders (from local polytechnics) get S$900 and degree holders (again, recognised universities) get S$1200, regardless whether you got MSc or PhD. You'll be getting this 'allowance' until you obtain your CPL/IR, which would be another 2 years from the time you join.