Best Mattress to buy for my study room

Looking to buy a good-quality mattress(Max 6k) for my study room and could use some advice.

Long story short, during some renovation work, a neighbourhood cat somehow got into the house and did... something to my current mattress. I won't go into details, but it's the only plausible explanation. Ever since then, I've completely lost confidence in that bed and haven't been sleeping well.

I'm based in Kochi and need to buy a replacement, either online or offline. I've come across brands like Wakefit, Emma, Sleepyhead, etc., but I'm struggling to understand the differences between mattress types such as memory foam, latex, coir, and hybrid mattresses.

A few questions:

• Which brands are actually worth considering?
• What's the real difference between memory foam, latex, coir, and hybrid mattresses?
• Are the 100-night trial/return policies genuinely problem-free, or is there a catch?
• Any stores in Kochi where Iit is more worth than online?

The mattress size is roughly 74" × 46" (not measured very accurately yet).

Nobody else in the house really cares about this decision, so I'm picking it myself and don't want to make an annoying mistake. Any recommendations or experiences would be appreciated.