The smallest Indian city that (almost) all Indians would know would be the hill resort of Shimla (pop 170,000). However, this is because a place is expected to have a population of about 100,000 to be declared a ‘city’, so for example New Delhi is only a town.
If you host your own instance, you have complete control over what gets posted. If not, you have to follow your instance’s rules.
That’s just basic bot detection, like a captcha. Karl Marx’s works are out of copyright, and Lemmy’s lead developer is a communist, hence the choice.
In general, instances don’t expect you to agree with their mods on politics or religion, but the content hosted on that instance would be somewhat biased towards the mods’ tastes. So you go from lemmygrad (far-left) to lemmy.ml (centre-left) to lemm.ee (centrist) to shitjustworks (centre-right) to lemmy.world (right-wing). Personally I’d avoid the first and last, but it’s up to each person to decide what’s right for them.