Hi
That area of pitting is where there is a hole in the gasket which allows the coolant from the block to contact the cylinder head. This is quite common and shoudn't be anything to worry about in your case.
Looking at your first photo, there seems to be a blemish under the intake valve of number 3 cylinder. Is this oil/grease or something? If it's a ripple in the aluminium I would worry more about that as it is where the cylinder gasket will sit.
Tim
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