Hi can anybody help me I have to determine if PQRS is a parallelogram and then find the area

1- P (1,1,1) Q (-2,3,-2) R (-1,0,1) S (2,-2,2)

2- P (-1,1,1) Q(3,2,-2) R(5,3,-5) S (1,2,-2)

What is the procedure to do this?

Also i have to determine the area of the triangle P(4,-1,3) Q(1,-5,2) R(1,1,-6)

One last thing what is the formula to calculate the angle between 2 vectors when is a 3d vector?

any help will be appreciated it

thanks