Issues with old Eclipse IDE release pages

As reported on the planning-council mailing list by @jograham, there are a couple of issues with old release pages:

Links should always point to the correct release and not the "latest" release links.

• https://www.eclipse.org/eclipseide/2018-09/ => Page is missing and shows a 404 ❌
• https://www.eclipse.org/eclipseide/2018-12/
  • Links point to the 2018-12 release 👍
  • Nitpick: "The next Eclipse IDE release is coming in 2019-06" => should be "[..] 2019-03"

The following issues

• "Download <year>-<month>" button points to https://www.eclipse.org/downloads/packages/installer ❌
  Should be https://www.eclipse.org/downloads/packages/release/<year>-<month>/r (or is there a release specific website for the installer?
• "Other Packages" buttons (2 buttons!) point to https://www.eclipse.org/downloads/packages ❌
  Should be https://www.eclipse.org/downloads/packages/release/<year>-<month>/r
• "Documentation" button points to https://help.eclipse.org ❌
  Should be https://help.eclipse.org/<year>-<month>/index.jsp

appear on:

• https://www.eclipse.org/eclipseide/2019-03/
• https://www.eclipse.org/eclipseide/2019-06/
• https://www.eclipse.org/eclipseide/2019-09/
• https://www.eclipse.org/eclipseide/2019-12/
• https://www.eclipse.org/eclipseide/2020-03/
• https://www.eclipse.org/eclipseide/2020-06/
• https://www.eclipse.org/eclipseide/2020-09/
• https://www.eclipse.org/eclipseide/2020-12/
• https://www.eclipse.org/eclipseide/2021-03/
• https://www.eclipse.org/eclipseide/2021-06/
• https://www.eclipse.org/eclipseide/2021-09/
• https://www.eclipse.org/eclipseide/2021-12/

I guess it should be a regular task once a new release page goes live on GA day to adapt the links on the "current release - 1" page.

@jograham: Please add any missing or wrong links that you found/find.