Watch this tutorial to learn how artstudio supports multiple open documents:
https://m.youtube.com/watch?v=CKI8eEZbz9w

Open Brush Editor, go to Dynamics section, and disable dynamics you dont like.
If exitor is in „thumbnail only” mode tap segment button in top right corner
You can finally overwrite brush or save it as a new brush - to do it tap ‚+’ icon

Celebrating the Mundial in Russia Ilya Tuljakov created this:

1) Sorry, it is not possible for the moment. Some vector operations are planned for a future.

2) Clipping Mask can be applied to both single layers and a group. So you can put few layers/cliping mask into a group, then add adjustment layer over the group and enable Clipipng Mask for it.

We are not going to add any new tools in the next major update 1.3.  We will consider adding this later

In my opinion the only solution is to add 'Multitouch move/scale/rotate' is to just one more mode to Transform Tool. Currently there are Scale, Rotate, Move, Skew, Perspective, Free. I will consider adding 'Multitouch' here.

Eyedropper - you can activate Eyedropper tool with icon in left toolbar. I'm considering Eyedropper icon in fullscreen as well

Overlapping filter/adjustment view - i agree, i will consider moving it to the right edge (when ipad is in horizontal orientation).

Grey interface - i agree as well, i will soon make the background darker and the icons brighter.