Which of the hacking methodology steps can be used to identify the applications and vendors...

OSINT (Open Source Intelligence) refers to the collection and analysis of information gathered from public, freely available sources to be used in an intelligence context. In the context of hacking methodologies, OSINT can be used to identify applications and vendors employed by a target organization by analyzing publicly available data such as websites, code repositories, social media, and other internet-facing resources.References:

Michael Bazzell, "Open Source Intelligence Techniques".