Question

There is a combination lock with four inputs 0-9. Can you figure it out?

The second isn't a 6.

Only one digit starts with a vowel.

The fourth is greater than the first, is greater than or equal to the third, and is greater than the second.

Either the first two numbers are even & the last two numbers are odd or vice versa.

The difference between the 1st & 2nd is the same as the difference between the 4th & 3rd (order matters).

One of the numbers is prime; three are composite.

Answer 1

8- 4- 5- 9

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primes- 2,3,5,7, composites- 4,6x,8,9, neither prime not composite- 0,1
excluded - 6 as per condition 1, so three of composite numbers are 4,8,9 as per condition 6
9 is the last and 8 is the first, because the fourth numbers must be the greatest of four as per condition 3.
4 must be second, if it is the third, then 9-4=5 and 8-5=3, makes the order 8,3,4,9 but first and last two numbers must be both even or both odd as per condition 4.
8,4,x,9
x=9-(8-4)=5
8,4,5,9 meets all conditions