Insect mesh and air gap for timber cladding?

[Great_scot_selfbuild]

Question for those who have installed (or had installed) timber cladding…

 

I know we need an airflow behind the cladding, and because we need to fit our shingles onto horizontal battens, we have vertical battens followed by counter-battens.

 

I’ve 2 questions:

 

1. How large does the gap at the bottom and top need to be?
2. What have you used for the insect mesh at the bottom and top?
3. Does it matter if the top and bottom of windows doesn’t have a gap? 

 

Around the windows, our builder has installed double-thickness battens, which is good for the fire stopping, but limits airflow - however, because we have counter-battens, there is still airflow laterally and the windows don’t cover the full wall, so does this still meet the requirement?