1. By what time shared taxi/bus start from NJP to Gangtok? I'd be reaching NJP station at 4am.
2. By what maximum time should we leave for Lachen from Gangtok? Is leaving at 12pm fine?
You will get from 5,if season time then may get even at 4.
Starting for Lachen dont depends on you but the travel agent, normally tour starts around 9-10 am.