The two 1957 SC stars are so common, I'd say $2.50 for the pair, if any premium, and the 1935A SC NA, I'd guess maybe $20.
I picked these 2 up a bit back. these are special commemoratives from the Bank. Several banks have had these over the years and later on they tend to sell at a premium. The cool thing with these is HK has no normal 150$ denomination. The last 2 photos show the current HK currency of 10$, 20$, 50$, 100$, 500$ and 1000$ These are not just sold to the public you must enter a raffle online with the bank and only like 1 of 100 people were selected to received. I was not a lucky one and picked these 2 up at a coin show shortly after.
Fairly affordable, actually. I won that at auction for just $19. You can find them as Buy It Now on eBay for usually ~$30 or so
Not entirely sure, I didn't find it in Krause and PMG has it listed at $100 O.O I would imagine value is in the $30-$50 range, though. $100 seems a bit high