YES! It will help retain MUSCLE and is calorie free so will NOT hinder fat loss

No test needed, this is common sense

It needs to stay in ketosis, so this is the only option

YUP--mixing Barracuda with CLASH is recommended

I do not believe in measuring heart rate as it varies per person. Just go until the time is up!

https://www.stack3d.com/2017/07/machine-sleep-aid.html

Since your knees are straight, I have no idea why this would happen.

I would work the core, see this: 

And just train normally!

I think carb cycling is silly and not needed

Some success, yes. But you'll be limited by lack of ways to progressively overload