Consider this grammar: \begin{array}{l} S \to aabBba \mid aAb \mid aab \\ bBb \to bCa \mid aaa\\ aA \to aC \mid bba\\ C \to aab \mid Cb \end{array}
This is clearly context-sensitive (CS). It's not context-free, and it's not regular. But I'm wondering if because it's CS, this means it's also unrestricted (since it falls under that in the hierarchy). Would this be considered CS?
Everything you stated is correct. It is CS and unrestricted.