The major similarity between the two documents is that both of them are limits on the power of the government. A secondary similarity is that they are both written contracts of sorts that spell out what governments can and cannot do.
The idea that a government can be limited was a novel one in the 1200s. The theory of monarchy was that every ruler had unlimited power subject only to whoever was above him (and the king was subject only to God). But this document said that there were earthly rules kings had to follow.
The Bill of Rights does this as well -- it sets limits on what a government may do.
A piece of paper is 3-D.
The main question and the supplementary question are two very different questions from two very different fields. I will answer here the supplementary question. That is:
Is a piece of paper considered to be a 2D object or 3D object?
Strictly speaking a paper is a three dimensional (3D) object, as it has length, with and thickness. However, for most practical purposes, the thickness of paper being very small as compared to its length and width, paper is considered to be a two dimensional (2D) object. Further when we consider paper as as something to write or print on, we are only interested in the two side or surface of the paper, and these surfaces have no thickness. This is another reason why a paper is considered to be a 2D object.
Without going into details of the first question, that is, similarities between Magna Carta and bill of rights, I will say that the tow are about as similar as a freshly laid egg and the chicken that comes out of this egg. Magna Carta represents one of the earliest form of legislation that placed some checks on absolute rights of the King, that over a period of centuries developed into various legislation such as Bill of Rights, intended to define and protect individual rights and freedom.