Facebook gaming is huge platform that exists within the Messaging platform. While they may have consolidated from a standalone app to a service in an existing platform, that is not a "fail" by any measure.
The same goes for Facebook Events, which is hugely popular within the Facebook platform.
I understand what you asked for, but it's a distinction without a purpose as indicated and just by that measure is misleading.
Many of these experiments are intended to start out as standalone apps that have their best features folded back into the main product and the user's transitioned over. That's by design. Framing it as a failure is not reasonable from that perspective.
This is especially true of many of the products you listed that are arguably some of the most used function of the main platform like messaging, gaming, and events. They all contribute a significant amount to the DAU for Facebook.
The same goes for Facebook Events, which is hugely popular within the Facebook platform.