No.
Never.
No, never.
No, two odd numbers cannot have a greatest common factor that is an even number, because no odd number can have an even number as a factor. Any even number multiplied by any other whole number is always an even number.
No, 2 is a common factor of all even numbers but not necessarily the greatest common factor. Take 40 and 32: 40:1,2,4,5,8,10,20,40 32:1,2,4,8,16,32 8 is the greatest common factor of these two even numbers.
No.
No. Odd numbers only have odd factors. They could not have an even factor in common.
No, the GCF of 6 and 7 is 1.
No, always odd.
No, always odd.
No. Every even number has a factor of 2. So any two even numbers share 2 as a factor. So the greatest common factor has to be at least 2.
The GCF is 2.