I'm sorry but I can't read your text

to #5:

I assume that you mean P(1, -2, 0), Q(3, 1, 4) and R(0, -1, 2).

You need a fixed point (I take P) and 2 direction vectors:

Then the equation of the plane is:

As a parametric system of equations:

The normal vector of the plane is:

And therefore the equation of the plane in normal form (keep in mind that the point P belongs to the plane!):