Almaz had a 23mm cannon [1].

[1] https://en.wikipedia.org/wiki/Almaz_program#Defense_measures

Yes, but again that was a conventional weapon, and would have been fine under the treaty. I don't exactly condone it but it was also crap and never flew again. This video https://youtu.be/e-n_V5iEwAs goes into some of the reasons it was a particularly crap idea