I am from India, studying in the UK. I have a B1/B2 USA visa. I haven’t travelled to the USA. Is it possible that if I can travel directly to Mexico from the UK without entering the USA, by using the USA visa?
Yes. There are plenty of flights that allow this from the UK, and if you have a visa from countries such as the US like mentioned you can use this to enter Mexico.
if you have a valid visa for countries like the USA, Canada, Japan and the UK, or if you have a valid Schengen visa, you do not require a separate visa for up to 180 days of stay in Mexico. (source, another source)
Things to note: Your passport should be valid for 6 months beyond arrival, and you should check if the US visa the appropriate type. If the nature of your visit is tourism, you should have a visa that falls under this category for example.