Works fine throughout the range on my 10-20 wide angle lens on a cropped sensor. Although I suspect that 10mm would be the absolute limit, any wider and I think vignetting would occur. I don't use the extreme 10mm end that often however I was expecting some vignetting but I seem to have been lucky and gotten away with it. This is a really nice set of filters. Hope this helps. 

So with my sigma 10 20, only a little with 11 mm but no longer visible with 12 mm (aps-c) 

Hello, unfortunately no, the screen on time can be set to 5 seconds, 10 seconds, 15 seconds or 20 seconds. 

Yes. I have the same lens and adaptor on my Sony a7ll and it works beautifully. The m42 is also known as the 'universal' mount as other 3rd party camera and lenses also used it. I own 6 other K&F e-mount adaptors to different lens makers (ltm, MD, CF/CD, Nikon) and they all are well built with a nice snug fit. Highly recommended. 

I actually have not received this adapter yet. It's shipping from China. Don't think that was disclosed in the ad. However, I do not believe this is for the Pentax Q body rather for digital and film cameras that take the Pentax K mount in its many variations. So I'm expecting to be able to mount my Leica M mount lenses on my digital and film Pentax K mount cameras, no autofocus or relay of exposure information, only to be used with manual focus and exposure.