Apple watch ultra

I did not say that at all. I said Apple watches sold in the US are engineered to connect to carriers who support Apple Watch in the US, Canada, Mexico and Puerto Rico. There is NO carrier lock. Any carrier in those countries who support Apple Watch can be used on a watch purchased in the US. Then there's the rest of the world. Apple watches purchased outside the US, Canada, Mexico or Puerto Rico, will be able to connect to any carrier in the rest of the world who support Apple Watch.

And you are also incorrect in that iPhone is not now, nor has it EVER provided a worldwide warranty. iPhone Warranty may (and almost always is) limited to the country of purchase.

That's a question you should ask your carrier in India. Apple sells Apple Watch by region. And be advised an Apple Watch Ultra purchased in Japan will not have warranty in India, so it could be quite expensive to travel to Japan for warranty service if it is needed.

Buy your watch in your country and you won't have ANY issues.

You're very welcome.