Clue-1 + Clue-2 + Clue-3 ===> 7, 9, 1, 8 are possible numbers {order is not considered here}
assuming 7, 1, 8 are the correct 3 numbers {order is not considered here}
Now from Clue-4 + Clue-5 we can rule out 7 as the correct digit in the final code.
Now 9, 1, 8 are the only digits left. The only thing left out is its order.
from Clue-3 + Clue-1 the order has to be 8 1 9.