Russian Fluency Fast Track

Will I encounter the same nouns with a different grammatical case? or all nouns are unique? (in the Fluency Fast Track)

Yes, in Russian FFT you will encounter the same nouns with different grammatical cases. I believe that currently, when Russian sentences are put into categories according to their cloze words, Clozemaster never makes an attempt to treat different word-forms of the same dictionary form of a noun as if they were the same word. For instance, in the “X most common words” categories, if a dictionary form A has different word-forms B and C, the frequency of B and the frequency of C are counted separately, as if they were unrelated words.

Here are search results to demonstrate that the different inflected forms of вещь are treated as separate words in FFT: