A few questions regarding bed leveling

Before anyone cjhomps on my noggin, I have read Carl's peice above and a number of other posts on this and other forums along with watching Chuck Hellebuyck's videos and others.

I finally installed my printer (a 1.0A) and am happy with the results I have gotten on my first few prints straight from the box. Only flaw I came across was the bottom right bearing being a little loose which I have shimmed.

My questions are

1 How much difference is there in leveling a hot bed to leveling a cold bed.
2 Can you level the bed and then readjust to take into account the gap between the extruder head and the bed?
3 If you have a know deviation for the gap can you level the bed at the bottom of the z axis?
4 Once a bed has been leveled can I mark the position of the thumb adjusting knob (say with twink so that should it begin to rattle loose it can be quickly put back to it's home position.
5 What are the other variables make the bed go out of alignment / level?

Basically what I am asking is can the bed be set back to a known position that should be level / aligned when cold. If this the case then a stop set could be designed to ease the burden of leveling.

As I am new to this I know that others will have played with the concept I am describing so rather than reinvent the wheel thought I'd get others experiences / recommendations so that I can ponder with more than pure speculation.

Mant thanks for your help in advance

Dave