Layout from PSD layout. How to layout correctly?

Question

css

Layout from PSD layouts, as a rule, is not explained anywhere, it is believed that a person should understand everything anyway. As it turned out, not everything is so simple, so I failed the test task when applying for a job.
When developing the layout, I had a lot of questions and still do not get out of my head, namely:
There is a layout with a size of 1920x2280.
1) How to determine the rubber parts on the layout, if this is not discussed in advance?
2) If they throw off one high-resolution PSD layout and ask for adaptive design, then you can invent anything for mobile phones and tablets?
3) In what units of measurement is it better to typeset for ie9+ support?
4) If there are three layouts in sizes 320 , 768 and 1920, is this meant to be the minimum width of the monitor, so a layout of 768 at 767 will already look like a layout under 320?
Please help me figure it out)

Answer 1

1) guided by common sense
2) it is possible, guided by common sense
3) it is obvious that each unit of measurement has its place.
4) these are control points. the designer lets you know how things should work. at these points, as a rule, the layout should match the layout. the rest - guided by common sense.