I want to know how embassies verify flight bookings made with travel agencies? I made a reservation with a reputable local travel agent and was only given 1 PNR code among my 8 bookings. There is a reservation code, though. According to the agent, “All Embassies are connected to IATA that’s why they can see the flight blocking.” How true is that?
The PNR code and your name are enough to locate your flight in the international booking systems like Amadeus. The wording used by the embassy is a bit sloppy though ("connected to IATA"). All international flight are operated by airlines who are members of the IATA and follow its regulations. Such flights must be registered in one of the big international booking systems. The PNR code is the reference number used in those systems. The embassy may have extra privilege (acting like a travel agency) and therefore can see personal details.
Probably they doesn't. But they see a lot more flight booking than you, so they could check further, in case of doubts. And they are used to receive fake documents.
Website of airlines permit everyone to check the status of a booking (booking reference, name and dates are available on booking document), connecting to IATA is also not difficult, and this possibly is done indirectly: embassy will put your data in a central system [on embassy country], which also control booking. This data is used also for other checks.
Note: sn embassy usually have few airlines to check: (local airlines and national [of embassy] airlines; long-flight airlines are not so many), and it will make extra check if you book a very strange journey to reach destination nation.
Remember: the authorization to enter in a country is given by immigration officers, so if you enter in other ways, they could verify the reasons, and if they find a fake booking on origin, you will not be able to enter.