Efficient way of finding distance between two 3D points

Question

I am writing a code in C++ and want to compute distance between two points. Question 1:

I have two points P(x1, y1, z1) and Q(x2, y2, z2) , where x,

Answer 1

Q2 answer: x1 = x2 and y1 = y2 and z1 = z2 if the points are the same.

Taking in consideration that you store points as float/double you might need to do the comparison with some epsilon.