Also, I doubt China will be very happy about this boat going to sea as, quite obviously, they're the logical reason for this boat to be built in the first place.
37 years for the whole programme.Don’t expect the sub & it’s design to be that old.Firstly,I think work on a design itself started in the late 80s after India leased a Soviet boat..I believe atleast 3 design variants,starting from a copy of the old Soviet Charlie-II to a smaller indegnious design in the mid 90s were evaluated.From the looks of the artist impression(by no means definitive),it seems to borrow a bit from the Russian Akula class submarine.
No matter how good your engineers/architects,if the policy makers & strategists don’t know what they want,you will never get there.