We see the world from a human perspective. All the laws, all the flaws. It's based on our discoveries, our observations. Otherwise I wonder if we're even the most evolved species. Many bacteria are better adapted to survive in conditions which are extreme in our terminology, Like they can survive in extreme climatic conditions, can live w/o oxygen etc. Infact they can even invade us, compete us for our own machinery and defeat our immune self, if we don't take foreign aid. Looks like we're just the most complex, not most evolved as we like to believe. But unfortunately or fortunately, those bacteria can't come and argue they're better/ more fit.
Cosmetic surgery is an artificial approach, so it's indeed against the nature. Other than that IDK much about whether its process is mutagenic or not. Since it's not a routine procedure, I think it's less likely to contribute much to gene pool. Unless it's potent enough to cause a sudden evolution.
Marriages in same caste, arranged or not - If this continues for several thousands of years more, each caste may separately evolve into a new species. Divergent evolution of Homo sapiens sapiens. Unless there's a break in practice after every few generations. Then that break would include other variants in the pool and not hinder normal evolution.
In cosmetic surgeries, arranged marriages or other forms of human interference, nature's collateral damage. We don't aim to purposefully harm it, our lifestyle is such we thrive on artificial aids. We live disconnected from nature and don't think about the effect our actions have on it or on ourselves for that matter. Number of casualties and types of diseases have increased multiple folds in the years of our civilised existence. We don't think of uprooting the basic cause or pay attention to root disturbance because we have external aids to sustain ourselves, however superficial. But, when it comes to natural calamities, we stay helpless. Had we not civilised and lived with our mammalian instincts, we'd have surely been more attuned to nature. But now the condition is such that any severe exposure to natural stuff is intolerable to us, be it sunlight or normal dust.