Chenonceau:

Some papers have...

(1) spelling mistakes
(2) ambiguous questions

Schools like Nanyang, Tao Nan and Rosyth have very difficult Math questions. We do these FIRST and use them to learn with in a low stress context, way way way before exams. We leave the easy Math exams (e.g., MGS and CHIJ) for just before exams to build confidence and drill for speed.

ACS has very good English papers. One particular comprehension question and passage stood out for me in the subtlety of thought required for inference (and yet the question was not ambiguous). For English, we only do ACS and leave the rest. For Science, RGPS has highly thoughtful questions with multiple answers sometimes. Just this one paper alone teaches a lot about the thinking processes/skills required for Science. No need to do all.

Thanks for this tip, Chenonceau!!
I've got 2010 & 2011 papers. Now I'll just narrow it down to the ones u've mentioned.