What are the rules that help distinguish between similar verse endings such as "إِنَّ اللَّهَ غَفُورٌ رَحِيمٌ" (Indeed, Allah is Forgiving and Merciful) and "وَاللَّهُ غَفُورٌ رَحِيمٌ" (And Allah is Forgiving and Merciful)?

Every word and letter in the Qur’an is placed in its appropriate position, and this is an aspect of its miraculous nature. The verses in which words or letters change at their conclusion are suited to the meaning for which the verse was revealed. These can be accurately recited by contemplating the meaning of the verse that concludes them, and by frequent repetition and review. Allah has made the Qur’an easy to memorize, and there are books that help in accurately reciting similar verses.