Apple Watch series 5 GPS+Cellular

Cellular radios are regional, so for example the North American Apple Watch will not work in other parts of the world

ECG is very country specific, as it is considered a medical device and must have approval(s). The governments (plural) Must have approved ECG in the country of purchase And the country where used. The biggests complaint about ECG is buying in Dubai and trying to use ECG in India. It seem Dubai is a common stop on flights to India.

There may be other restrictions in the country of purchase that will carry over to the country where used.

The Warranty is Not international.

Cellular Carriers that support the Apple Watch, which models, the radio frequencies each model uses, and the country where they offer service:

https://www.apple.com/watch/cellular

Apple Watch ECG countries

https://www.apple.com/watchos/feature-availability/#branded-ecg

Apple Watch Feature Availability by country

https://www.apple.com/watchos/feature-availability

Yes, The Apple Watch GPS+Cellular Models are Available to use in another country if it meets the following 2 statements:

1. The country and carrier you are using is listed under here: https://www.apple.com/watch/cellular/#table-series-5
2. You did not buy the Apple Watch from Foreign Country With a Carrier such as AT&T.

Thank You

Check the previously posted link for cellular carriers. It will tell you what Apple Watches are sold in in what country. Just compare Hong Kong against India.