O Zayn! The short answer to what you asked about the verses is that changes have been preserved because in the early days, the grammatical rules of the people were never observed at the time of the revelation. Today, these rules are observed on account of wisdom. Therefore, if a tablet was recited before the Countenance previously, and he reveals in some places something different than what he revealed previously, this has to do with outer expression. In reality, both things that were revealed have been and will be correct.
In the Land of the Mystery, he had intended to reveal grammatical rules that are in the divine knowledge so that everyone would understand. He delayed on account of onrushing sorrows, continuous concerns, and successive tribulations.
On the occasions when most of the tablets were revealed, it was impossible to review them, and that which flowed from the pen of the servant attending the Countenance was dispersed near and far. Therefore, it is possible that in some cases there were omissions or additions and a little disappeared since no one is able to completely edit what is revealed at the time of revelation. Asking about these instances has been and will be beloved, although in the eyes of the Prisoner a new revelation is more beloved than referring to what was revealed previously. Referring to him (for a new revelation) has priority and is easiest, and he is the causer of causes.
Khadim Allah (Mirza Aqa Jan), on behalf of Baha’u'llah, to Zayn al-Muqarrabin. Amr va Khalq, 2:105-7.