What is the difference between facilitating the hamza and nullifying it in the various narrations of the Qur'an, given that both are recited as a yaa (ي)?

Written fatwas are not a way to learn the recitations (Qira'at); rather, reading and performance must be received orally from proficient reciters. Abu Ja'far facilitates the hamza in (Isra'il) and substitutes the hamza in (Ji'ta). The difference between facilitation (tashil) and substitution (ibdal) is that facilitation is creating a letter between the hamza and the letter that corresponds to its vowel sound, whereas substitution is placing a pure long vowel in place of the hamza. Facilitation is a change that affects the hamza in four ways: "bayna bayn" (between-between), substitution, omission, and lightening. "Bayna bayn" is the emergence of a letter between a hamza and a vowel letter, and "substitution" is the placement of alif, ya, and waw in place of the hamza. As for substituting the hamza, it is making it a pure long vowel, while facilitation is making the تحقق (realized) hamza between itself and the letter from which its vowel sound originated. Its pronunciation can only be mastered through oral transmission and reception from the shaykhs.