How to retrieve a specific revision?

Could someone assist me in locating or providing a clue for the following:

  1. The revision "r49619" for Version 2015.05?
  2. Source Code for "base files 157.2-r49619"?
  3. Where to find the Source Code for the "kmod" files for this version (revision / 2015.05)?
  4. Link and/or Source Code for the package "mtd" Version 21?

I received this information years ago, and now I need to undergo an OSS clearing process, but I'm having difficulty locating these specific components.

That version is so old that you shouldn’t spend any time on it. It has been unsupported for many years and has many known security vulnerabilities. Only the current releases should be used now.

Based on the versioning, that is from the "old OpenWrt", and after 15.05.1 release, likely/possibly from the SVN trunk.

Your best bet is the pre-merge source archive https://github.com/openwrt/archive

But it may also be a further/later OEM SDK based on that old chaos calmer 15.05 codebase.