Yes they interline, no need for a visa, you will be taken care of by LH ground personal when you deplane and taken to the international transfer desk to be verified by UL and then go thru transit security into the CMB gate area

The UL agent at the transfer desk will give you a lounge pass, you should be able to access the business class section of the lounge (most Indian contract lounges have different service levels for PP/credit card visitors and airline elite/C/F pax)