How to download old version of Flash Authoring tool?

if you have a cc subscription, you can install back to cs6 as part of your subscription via your cc app:

click the 3 dots at the cc app's upper right > preferences > creative cloud > tick 'show older apps'.

then: https://helpx.adobe.com/download-install/using/install-previous-version.html

pre-cs6 versions would be trials installed by direct download:

Single user licensee downloadable installation files available:

• Suites and Programs:    CC 2018 |  CC 2017 |  CC 2015.5 | CC 2015 | CC 2014 | CC 2013 | CS6 | CS5.5 | CS5 | CS4, CS4 Web Standard | CS3
• Acrobat:  DC, XI, X | X,X suite,9,9 extended | 8 | 7 |
• Authorware:  7.01 windows |
• Captivate:  11 (2019) | 10 (2017) | 9 | 8 | 7 | 6 | 5.5, 5 | 1
• Cold Fusion:  11, 10 | 9.0.2, 9.0.1, 9.0.0, 8.0.1, 8.0.0, 7.0, 6.1, 6.0, 5.0, 4.0 |
• Contribute:  CS5 | CS4, CS3 | 3,2
• eLearning Suter:  2.5 7z |2.5 exe |
• FrameMaker:  12, 11, 10, 9, 8, 7.2 |
• Lightroom:    6.14| 5.7.1|  4.4 | 3.6 | win 2.7, 1.4.1 | mac 2.7, 1.4.1 |
• Photoshop Elements:  2018,15,14,13,12,11,10,9,8 | 9,8,7 win | 8 mac | 7 mac
• Premiere Elements:  2018,15,14| 13,12,11,10,98 | 7
• RoboHelp:  2015, 11, 10, 9, 8

Updates

• non-cc updates
• CC (2013) Updates:
  •   Windows
  •   macOS
• CC 2014 Updates:
  •   Windows
  •   macOS
• CC 2015 Updates:
  •   Windows
  •   macOS

• Download and installation help for Adobe links

• Download and installation help for Prodesigntools links are listed on most linked pages.  They are critical; especially steps 1, 2 and 3 which also apply to eLearning Sute 2.5.  If you click a link that does not have those steps listed, open a second window using the Lightroom 3 link to see those 'Important Instructions'.

And a big thank you to Jim @ Prodesigntools for helping me with these links!