The Variability in conjugation of the verb “чтить”

The present study deals with the rival forms of the verb чтить. According to the Spelling Dictionary of Russian (RAS), the standard conjugation of this verb is following: чту, чтишь, чтит, чтим, чтите, чтят / чтут. The form of 3PL has two variants, while all others are ones of the IInd conjugation. The following questions arise: 1. How did it happen? 2. Does the verb чтить also have other variants for the rest of its forms?