Bug: Don't use multiplier equipment. When level up, the multiplier will reset to no bonus. If you change other equipment after level up, your multiplier will lower than you should be.
Full happiness 18 hours 90+95+100+100+100 engineers still not enough for 4 stars to 5 stars future chassis. This means that you need to focus on future chassis only(lose all your races) to get the 5 stars. Non-sense.
Wait for 150+ mobsters. 2 turns can take over 1 family. 1st turn: buy 1 land form other family, and attack all 3 other locations. 2nd turn: buy the land that family just get from you. That family will end.
Free flight: you need to change location to the last area. + maybe you need 1 billion cash.
I just complete the quest automatically when I move to Japan. I have 2.5 billion cash at the moment. This quest move me to New York free of charge, that is why it call free flight.
 "Little Protector Planes"){kind=icon}
 "Railway Valley Missions"){kind=icon}
 "Stormy Castle"){kind=icon}
 "Go Kart Manager"){kind=icon}
 "Heroes Empire"){kind=icon}
 "NYC Mafiosi"){kind=icon}
 "Office Story"){kind=icon}
 "GrandPrix Management"){kind=icon}
 "My Soccer Game"){kind=icon}
 "Painters Guild (Alpha)"){kind=icon}
 "Dutamasa Battle"){kind=icon}
 "Kids Vs. Ice Cream"){kind=icon}
 "Defender's Quest (lengthy!) Demo"){kind=icon}
 "Frantic Sky"){kind=icon}
 "Bitzy Blitz"){kind=icon}
 "Crystal Story II"){kind=icon}