Double your money hint:
After saving your game in any memory block, save your game in another block. Then, go to the bank, select money transfer, and transfer your money from one block to the others to double your money. Repeat to become rich.
Hidden animals hint:
To gain two hidden animals, purchase all five kangarooes and all five dinosaurs. After doing so, two new animals will appear -- a black kangaroo and a white dinosaur.