Slitherine

Immelmans? Barrel Rolls? These are staples of any air combat game. Documentation says nothing. I can't find through the UI how to do this?

Move the stick at the centre, then move it down to make an Immelmann/Split-S. This will reverse the aircraft heading by 180°.

You can make a 120° heading change by further moving the stick left or right.

Then you will have to decide if you want to perform an Immelman (by setting a positive altitude change) or a Split-S (by setting a negative altitude change).
After a few attempts at Immelmanns, you will notice that even the best WW2 fighter is not a F-16 .

I took the image from the game page and I think the image is slightly - but not significantly - different from the actual game interface. As far as I recall, the three stick position (straight, left or right Immelman/Split-S) are now aligned at the same level.

Awesome, thanks.

Next question. Is there an ability to side slip?

You're welcome.

As regards to your question, move the stick on the first notch on the left/right: the plane will sideslip one hex in that direction (this is considered as a "straight" move for tailing purposes).