Recently when I was watching one of your lecture on YouTube
in that last part of the video you said that if Allah swt had wrote Ayaat e Tatheer at some other place it would’ve been omitted/removed by the Bani Ummayya or by someone else while Allah swt says that He is the protector of Quran (15:9) so how can we make such claim that the Quran would’ve been changed?

Good question. So I was stating the different opinions scholars have and this is one opinion. This does not contradict the verse that says Allah protects the Qur’an. In fact it confirms it. Allah has promised to protect the Qur’an, and one way by which he protected it is that he put those verses in a place that he know the Umayyads would not change. So indeed Allah protected the Qur’an. The way the Qur’an is organized and structured helped ensure that it would be protected.