4579 is the smallest even number he can make
From left to right, pick the smallest possible digit every time. This will give you the smallest possible number.
The smallest four digit number is 1000. It is even so 1001 is the smallest four digit number that is odd.
The smallest is 1111 if repeats are allowed. If not, it is 1235.
-7510 is the smallest.
00000 or 00001