I mentioned Chinese suzerainty over Tibet to illustrate the legitimacy of Chinese rule vis-a-vis Indian's Northeastern states, a point which you debated. Regarding the so called violation of rights, it is not a simple yes or no answer. Put things in context, in the war torn era, no side will adhere to old agreement, its either you gain territory or you lose. This applies to every country. PRC was established as an unitary state, not a federation. Tibet had to be incorporated into China. However, it was accorded autonomous status rather than a province.
I bought up Mizoram air strike only to encounter you point that India did not use force, China did.
Since you know China is not democratic, the issue of electoral process is irrelevant. No, Tibet cannot have electoral process as it is incorporated into PRC, reasons I already mentioned in first paragraph. Lets be honest, India will never agree to a Kashmir plebiscite even if Pakistan and China willing to redraw the lines. Thats politics.