Hello.
I bought Pro because I thought the rest of the (Russian) grammar tracks would be like Nouns where it uses the base word and I have to choose the right case form. Pronouns, at least, doesn’t do that. Is there a way to change the multiple choice options?
Not that I know of, but I recommend the listening option as being good practice.
Well I can guarantee that if I were to start Russian, I wouldn’t be able to easily guess the multiple choice options 
This is to me one of the strengths of Clozemaster, it allows users of any level to start/continue learning any language here, by allowing a great degree of customisation with regards to difficulty.
For instance, you could make it more challenging by switching to text input (mind, for for example Russian I guess it would be easier practicing using the app, with a Russian keyboard installed/downloaded), with or without any kinds of hints (text box length, letters turning green/red).
Also, one of the best features of Pro according to me, is that it offers you unlimited Listening and Speaking learning and reviewing modes, as @Dcarl1 also mentioned.
Furthermore, you can create (and then play) your own collection(s), or those already added by others.
However, something which I would have really appreciated, but isn’t provided, is the option to indeed specify the exact options that will show up for a specific individual multiple choice sentence. You can select to use only “cloze words” as multiple choice options (instead of “random”), when adding a custom collection, but unless you made very tiny collections, of four sentences, where each multiple choice option were the cloze word of one of each of these sentences, it doesn’t currently seem possible.