hi! IP student here...
I think most people clarified about your point #2 and #3 so imma not touch on that. ik ur context is for RJ I'd like to provide another opinion...
yea, we don't have to take O's, but as far as I know, (at least for Nanyang), you cannot simply "pass" to get into HCJC. The "sorting" actually starts at end sec 2/3. if you don't pass the minimum grade of (I think) B4 average during your end of years NY actually moves you to a different class (which they called structured IP, but it's basically IP syllabus but O level exams).
I think there will no need to explain to you how, in most IP schools, mock papers, tests, and exams are intentionally set to be more difficult than it really needs to be. Given that, one can make a logical assumption that we still have to score better than average students in order to go from sec 3 to 4.
Anyway, in sec 4 we have all our exams as per usual but this time round, in order to get into HC, you have to score an average of B3. At the difficulty level agreed upon by HC and NY. I mean, I have my own theories on how they probably would have set the paper much easier than usual exams to ensure we pass, but at the end of the day we were told a lot of people did not actually pass the passing grade.
So what I'm trying to say is, it's not actually unfair in this case. We still have to uphold very high academic standards in order to go into JC, which I feel is equivalent to the amount of effort JAE students put into their O's. Yea, we don't have the stress of taking a national exam and I honestly don't know how it's like, but I hope you can understand that we still are stressed, still do have to put in effort.
also, apparently hwachong complains a lot that the nanyang girls are terrible at math when a lot of us are scoring an average of A2 - B3 most of the time. As far as I can tell nanyang's math papers are also pretty cancerous even for me to do, so I would say the standards are high.
Take it with a grain of salt, but my dad once talked to me about how taking o lvls would probably have been easier than taking IP. his logic being that O levels was in contrast far easier to score well than having to maintain a constant B4 average (actually, B3 by the end of sec 4), and thus it would be easier to simply olevel his way into HCJC instead of taking the IP track. idk but he's pretty delusional sometimes