This may be too late for you, but just thought I can answer your questions, coming across them. (My first post here~!)
You probably saw the eBrochure from the SIA website.
The recruitment process is quite close to what you read there.
1) First interview
2) Written test
3) Second interview
(Or more. There MAY be a public speaking segment depending on what you're going for)
4) Medical checkups (everything above is cleared already)
5) Admin, offer letter, etc
Yes, your friend is correct.
There is an english essay question in the written test.
It's like General Paper. Open-ended. Argumentative essay. There are 3 topic questions to choose from, and you'll have to write 500 words for it. Followed by a precis (summary) of a long passage.
My advice to prepare for this segment: Read newspapers, ChannelNewsAsia, etc, to be informed about general affairs and keep your english momentum flowing.
The other parts of the exam has maths, inference, abtract questions. Altogether, the process will take a fierce 4.5 hours. (some positions' requirements may skip a section, or add a section)
The interviews are quite straight forward, although it depends on the interviewers. But most likely the standard questions like your qualifications, achievements, interests in SIA, what you can contribute in, etc.
The 2nd interview will be more stressful cuz it's higher management, vice-presidents. But just stay calm and maintain your composure or stand.
Hope this info helps.
It's true, for SIA interview process.
For credibility, I went through all of the above the past 2 months.
I went through the public speaking part too. It was a debating session, where we're given a politically ambiguous topic to talk about.
Not sure which position you're going for, but GOOD LUCK~!!
If you are true to your values until the very end, falsehood cannot exist.