$1$. The only even prime is $2$ and all other are odd primes.
$2$. Difference between two odd numbers is always even.
First posted as hint but now @Cato asked for a proof so here We go:
Proof of $1$:
Suppose that there is another prime which is even (other than $2$), then it must be of the form $2k$ where $k$ being a positive integer, so that prime number can be written as $2 \times k$ which is enough to say that it is composite (Or not prime). A contradiction.
Proof of $2$.
As known (I don't think it also need a proof), every odd number is of the form $2k+1$, where $k$ is an integer. We just have to calculate the difference b/w two odd primes (Remember the word odd) so let first one be $2k_1+1$and second one be $2k_2+1$. Difference $= (2k_2+1-(2k_1+1))= 2k_2-2k_1=2(k_2-k_1)=$ even number.
I think it is enough. :) :)