Am I not allowed to work from home for one day in a month in case of an emergency, without raising an exception?

I don't know what's the big deal of not going to office. It's been 6 months since I joined TCS, last month I have 9% wfo index, this month I will have 10-15% max.

Before thinking about taking any action, think about the worst outcome.
What can happen?

1. 0 variable? It's as good as nothing so no worries there
2. HR might reach out to you on official mail with manager in cc and ask you why you aren't going to office. Mention some reason like client meeting times, mental stress, distance of home from office, injury, whatever.

-- the point is understand the dynamics, will they fire you on this? Highly unlikely, yet even if that's the case in 0.1% probability, are we so incompetent that we can't get a job in 1 month with 20% hike minimum?
It's quite easy.

Anyway, the summary is if u don't wanna do something don't do, just think of worst extreme cases and be prepared.
Example - Vijay Malya was the "King of good times", every actor, politician in India bowed his head infront of him for 10-15 years when he was earning billions via back channels and was it worth it?

100%, no it was worth 2000% for sure. He is still living as a king last I checked, no one who can touch him.

Ur calculation is right. You can WFH for 3 days in a month. But no TL, manager will officially tell you. They want everyone to wfo. So either they will tell you to apply leave or wfo. You can tell them that you will manage your 85% wfo.

Yes you can WFH without raising exception. Also it depends on your project as well

If you miss 3 days per month then also you will have attendance above 85% so it doesn't matter for 1 day as you still have 95%