-4309278
It is difficult to interpret exactly what you are trying to ask. If you allow your five digit number to have leading zeroes and do not allow negative numbers, then 00000 - 99999 = -99999 is the smallest number. If you do allow negative 5 digit numbers, then (-99999) - 99999 = -199998 is the smallest number.
012457, if leading 0s are acceptable. Otherwise, 102457.
4069
The biggest 4 digit number that can be made from using the digits of 850236, using a digit at most once, is 8653.
2
It is probably 247
34 .34 4(-9) 3/9
30468
-- If the same digit may be repeated, then 64 can be made. -- If the same digit may not be repeated, then 24 can be made.
9
If you can repeat a digit, there are 27. If you can't repeat a digit, there are only 6.