Ustadh, I know from the ulama are those that said not do recite the Isti’ādhah before reciting an Āyah for Istidlāl, but my question is, when I am revising I recite these Āyāt for Istidlāl and I want to get the reward for each letter, should I recite Isti’ādhah in that case because of my niyyah?

Ustadh AbdulAziz al-Haqqan

No, it remains the same. The istiadhah is not said for what is brought as istidlal, and your intention does not change that.