1)Nearest beach from CST is Marine Drive/Girgaum Chowpatty.Its 15 mins drive from CST.Take a taxi from CST directly to Marine Drive.From Marine drive you will definitely enjoy a walk to Girgaum Chowpatty.
2) It will take 1 hr from Girgaum Beach to BDTS.
3) From Beach walk towards Grant Road Station.From Grant Road take a local to Bandra.Both fast as well as slow locals halt at Grant Road and Bandra.From Bandra station Bandra Terminus is a 10 mins walk and autos are available.