the applicationID and app_version : for which application are you requesting a bundle? And for which version of that application. example for version "1.0.0" of appId "com.rdk.app.flutter-slide-puzzle" is represented by string "com.rdk.app.flutter-slide-puzzle:1.0.0" If you don't provide version, then default "latest" version is assumed
dacBundleFirmwareCompatibilityKey: this is unique ID that represents a set of firmware versions of a given platform for which the same App bundle is guaranteed to keep on working. example for 7218c platform this is the "1.0.0-41abf2fba994b2d04baedeca6d5adf097ece9f79" part of of "7218c_1.0.0-41abf2fba994b2d04baedeca6d5adf097ece9f79-dbg_dac_configs.tgz" file you see here . You can also retrieval current applicable "dacBundleFirmwareCompatibilityKey" of the STB from LISA when configured correctly in here