The English Blu-ray is legally available on Amazon (US/UK) and can be shipped to India. You can then watch it with English or Tamil subtitles (though the audio will be English).

Sometimes, dubbed versions of old Hollywood films appear on Indian ad-supported platforms for 30 days. Set a Google Alert for "The Three Musketeers Tamil streaming."

When you see Bd-ri attached to a Tamilrockers link, here is the technical pipeline that created it:

File size estimate: For a 2011 film in 1080p BD-Ri with Tamil audio, you are looking at roughly 2.8 GB.