Basudeba,
Thank you for reading and commenting upon my essay. I will answer your questions to the best of my ability.
You agree that time is not a dimension and you question the existence of extra dimensions. You ask for proof of extra dimensions. I have presented an accurate calculation of the size of the proton based upon a model that uses 5 dimensions. I argue that the accuracy of that calculation is circumstantial evidence in support of extra dimensions.
There are two i's in my essay. One is the complex i. The other is the unit vector i. They are not the same although they both satisfy i^2 = -1.
The thing that is puzzling you also puzzled me for a long time. Regarding quaternions, you state that i, j, and k are imaginary units. You believe this because they satisfy i^2 = j^2 = k^2 = -1. This thinking is incomplete. The unit vectors i, j, and k represent the x, y, and z axes respectively. The unit vectors make it possible for the axes themselves to be a part of computations. The unit vectors and the complex i can also be operators. For example, ij = k and the application of the complex i twice causes direction to reverse.
As an example, consider two simple addition problems. Let x = 1 and let y = 1. It follows that x y = 2. This is a simple scalar result. Now let x = i and let y = j. It follows that x y = i j. This is a vector from the origin of length sqrt(2) at an angle midway between the x and y axes.
Is this a physical description? Yes. Quaternions and complex numbers are used in computer programming. Quaternions produce rotations in video games.
Essentially, you must train your mind to think of the unit vectors as the axes used in geometry.
What my essay does, is combine physical space, in the form of an arbitrary unit vector, with the complex plane used by QM and GR. For the case of an inertial reference frame, it is very easy to visualize that combination as a 3-D universe.
I hope that clarifies your questions.
Best Regards and Good Luck,
Gary Simpson