Hey I got accepted into penrith and baulko last yr, reserve for Girra and if you have any questions feel free to pm me. If youre going to apply for a school that has HAST as a requirement you will have to sit it no matter what preference you put the school in. Your grades are decent and you might as well apply for all 3 as Girra/Penrith shares results meaning you just have to sit HAST at one school. To give you an idea of how my application was like, I did 3 clubs/societies including SRC and SRC, duke and debating are definitely really good. However you should try to join a few more if your school offers more. When it came to awards/grades i had a few distinctions in AMC and ICAS and other comps, top10% math Olympiad, Tournament of mind winner/merit ,zone sport award, rank 1 in 4 courses, dux, scholarship award, all A report with 1 B. In short you definitely have a chance and none of the schools are out of reach even tho baulko may be tougher as theyre based off supporting docs only. Try to get all A's for semester 1 and get involved with more extracurricular your school offers/ or volunteer in the community . Buy the ACER scholarship and HAST sample paper and try them out, do loads of reading comprehension/abstract reasoning /numerical reasoning questions, practice writing argumentative, expository, persuasive, creative, discursive essays under time limit and you should be well prepared for HAST (well thats what i did and it helped a lot). I also have a lot of resources/textbooks i used to practice for HAST, pm me if you want them.
Regarding the phs website question, It just means you sit HAST at your first preference HAST school, e.g you put Baulko at preference 1, penrith 2, girra 3, you will be sitting HAST at Penrith but the test results will be shared with Girra at the same time
Hope this helped, good luck!