Yes, since 10 is divisible by 5. Likewise, every number which is divisible by 9 is also divisible by 3.
Yes, since 10 is divisible by 5, ALL numbers that are divisble by 10 are also divisble by 5.
No - but all the numbers divisible by 10 are divisible by 5 !
No, not always. For example: 55 divided by 5 is 11. 55 divided by 10 is 5.5. It will divide, but not to an integer.
Since there are an infinite number of these, you cannot list them, but here's how you tell: Any non-zero integer which has one of the following in the ones place (rightmost digit): either a 5 or a 0