I am travelling from New Delhi to Mexico via Munich, having to connect flight at Munich. Will again return the same path 10 days later. Will I be required to go through immigration and therefore require transit visa for connecting flight at Munich if I do not go out of the airport? I am passport holder of India. I take Luftantsa, single ticket.
That's not quite the way it works. Since you booked your trip as a single ticket from Lufthansa, your luggage will almost certainly be checked through to your final destination and you won't need to go through immigration. But you might still need an “airport transit visa”, unless you qualify for some exemption (e.g. you have a valid US visa). See Do I need a visa to transit (or layover) in the Schengen area? for more details on the rules.
According to the German embassy in India, Indian passport holders need an airport transit visa, unless they fall into one of the exemptions (which you unfortunately do not):
Indian nationals generally require an airport transit visa for the Schengen area. This visa allows a short stop-over at an international airport only. Neither leaving the airport’s international transit area nor overnight stays in a hotel are possible. If you need to leave the international transit area (i.e. in order to catch a connecting flight at another airport to leave the Schengen area), please apply for a regular Schengen visa.
a) Indian nationals holding a valid visa or residence permit from a member state of the Schengen area or Bulgaria, Romania, Croatia, Cyprus, Liechtenstein, Ireland, UK, Canada, Japan, USA (except for holders of an US “Advanced Parole Document”)
b) Indian nationals holding a valid residence permit Andorra, Monaco or San Marino
c) Diplomatic passport holders generally do not require an airport transit visa.
The same rules appear in Timatic, the system which the airlines will use to determine if you can be boarded. In relevant part:
Visa required, except for Nationals of India holding onward tickets in transit through Cologne/Bonn (CGN), Frankfurt (FRA), Munich (MUC), Hamburg (HAM), Dusseldorf (DUS) or Berlin Tegel (TXL) AND meeting one of the following conditions:
- holding a valid visa issued by Bulgaria, Canada, Croatia, Cyprus, Ireland (Rep.), Japan, Romania, USA or United Kingdom;
According to this website you do not need a transit visa at Munich.
But according to the German embassy in the USA, Indian nationals DO need a transit visa, and I'd consider that a more authoritative source. They also list what documents you need to apply.
It's probably best to contact the German embassy in India (or one of the consulates) and ask there.