The article explains that: 1) relativistic formulas obtained in the existing version of the special theory of relativity (STR) are incorrect; 2) relativistic formulas obtained in the existing version of the STR are explained incorrect due to the use of the nonexistent in nature principle of light speed non-exceedance; 3) conclusions on physical unreality of imaginary numbers and existence of only our visible Monoverse drawn from relativistic formulas of the existing version of the STR are incorrect due to the use of the incorrect principle of light speed non-exceedance. In other words, the existing version of the STR created in the 20th century is not quite true. Moreover, the correct STR could not be created in the 20th century, since 1) the principle of physical reality of imaginary numbers refuting experimentally the postulated (i.e. being an unproven assumption) principle of light speed non-exceedance was published only in the 21 st century; 2) experimental data whose mathematical analysis discerned the quaternion structure of the hidden Multiverse consisting of twenty to twenty-two invisible parallel universes in six-dimensional space were obtained by WMAP and Planck spacecraft only in the 21 st century; 3) explanation of the way how astronomical observations of constellations of the starry sky in portals can experimentally prove the existence of invisible universes was published only in 2019. Therefore, the article presents an alternative version of the STR, free from the shortcomings of its existing version. Other relativistic formulas that have been obtained in the alternative version of the STR are explainable both at sub-light and hyper-light speeds, and for real and imaginary values of all quantities corresponding to these formulas. Therefore, the principle of light speed non-exceedance is excluded from this version of the STR. For the same reason, the alternative version of the STR states that there is a Multiverse of mutually invisible parallel universes, rather than a Monoverse, since all the mutually invisible parallel universes are relative to How to cite this paper: Antonov, A.A.