Singapore Airline-Transit for Level II Countries

I’m Iranian(One of the Level II Countries). I want to go to Australia. I am choosing Singapore Airline. It has 10 hours stop in Singapore. I want to know:

  1. Is it require to get a transit Visa? If so how much does it cost?
  2. Does Singapore airline offer a free Singapore tour? Does it need a different Visa and If so how much does it cost?