394 is the code to unlock the key.
If you take the second statement, 7 is incorrect from the first statement and 1 is incorrect from the fourth statement. Hence 4 is correct, but not on the second place. From the third statement, 4 is not on the first place. Hence 4 is on the third place.
From the fifth statement either 6 or 9 is correct. But combining it with the third statement, 6 is incorrect. Hence along with the first statement, 9 is correct and on the second place.
From the third statement, 3 is correct and on the remaining first place.