Hi,
I don't think there is an history of installed add-on versions in Firefox and we do not display the date of the versions on our web site.
If that helps, here is the list of the VDH/Firefox beta versions based on the xpi file name and date:
video_downloadhelper-7.1.3a10-an+fx.xpi 2018-02-12 19:59:55.707324552 +0100
video_downloadhelper-7.1.3a12-an+fx.xpi 2018-02-13 18:23:11.930029603 +0100
video_downloadhelper-7.1.3a13-an+fx.xpi 2018-02-14 14:38:55.392857612 +0100
video_downloadhelper-7.1.3a8-an+fx.xpi 2018-02-10 11:57:18.482566209 +0100
video_downloadhelper-7.2.0a2-an+fx.xpi 2018-02-21 16:18:37.643044102 +0100
video_downloadhelper-7.2.0a3-an+fx.xpi 2018-02-21 16:21:50.471041004 +0100
video_downloadhelper-7.2.1a1-an+fx.xpi 2018-02-22 16:09:14.473664951 +0100
video_downloadhelper-7.2.3a1-an+fx.xpi 2018-04-11 16:34:48.683064592 +0200
video_downloadhelper-7.2.3a2-an+fx.xpi 2018-04-13 16:06:09.380315818 +0200
video_downloadhelper-7.2.3a3-an+fx.xpi 2018-04-28 18:58:30.603326680 +0200
video_downloadhelper-7.3.0a1-an+fx.xpi 2018-05-16 17:36:14.914418401 +0200
video_downloadhelper-7.3.0a2-an+fx.xpi 2018-05-19 09:45:40.770707445 +0200
video_downloadhelper-7.3.0a3-an+fx.xpi 2018-05-26 18:42:14.700472789 +0200
video_downloadhelper-7.3.10a1-an+fx.xpi 2020-04-02 16:31:22.533270437 +0200
video_downloadhelper-7.3.1a2-an+fx.xpi 2018-05-30 11:37:57.763329013 +0200
video_downloadhelper-7.3.2a10-an+fx.xpi 2018-07-04 22:40:17.058103553 +0200
video_downloadhelper-7.3.2a11-an+fx.xpi 2018-07-09 10:27:02.547869423 +0200
video_downloadhelper-7.3.2a12-an+fx.xpi 2018-07-10 00:37:08.919049897 +0200
video_downloadhelper-7.3.2a13-an+fx.xpi 2018-07-10 10:19:50.322488168 +0200
video_downloadhelper-7.3.2a1-an+fx.xpi 2018-06-11 11:15:57.082691845 +0200
video_downloadhelper-7.3.2a3-an+fx.xpi 2018-06-13 18:19:35.915507039 +0200
video_downloadhelper-7.3.2a4-an+fx.xpi 2018-06-14 00:19:44.419159853 +0200
video_downloadhelper-7.3.2a6-an+fx.xpi 2018-06-21 14:25:47.372626846 +0200
video_downloadhelper-7.3.2a7-an+fx.xpi 2018-06-29 13:40:28.233564943 +0200
video_downloadhelper-7.3.2a8-an+fx.xpi 2018-07-04 09:29:46.686865622 +0200
video_downloadhelper-7.3.5a1-an+fx.xpi 2018-07-22 00:15:46.038412122 +0200
video_downloadhelper-7.3.6a1-an+fx.xpi 2018-08-01 17:01:59.615560103 +0200
video_downloadhelper-7.3.7a1-an+fx.xpi 2019-06-14 09:40:37.958532658 +0200
video_downloadhelper-7.3.8a1-an+fx.xpi 2020-03-03 09:45:24.170527408 +0100
video_downloadhelper-7.4.0a1-an+fx.xpi 2020-04-21 16:35:43.078414588 +0200
video_downloadhelper-7.6.0a1-an+fx.xpi 2021-05-18 19:10:40.783304126 +0200
video_downloadhelper-7.6.0a2-an+fx.xpi 2021-05-25 16:46:12.175838941 +0200
video_downloadhelper-7.6.0a3-an+fx.xpi 2021-06-27 07:11:04.301164070 +0200
video_downloadhelper-7.6.0a4-an+fx.xpi 2021-06-29 22:51:23.408779028 +0200
video_downloadhelper-7.6.1a1-an+fx.xpi 2021-07-03 11:26:07.846836289 +0200
video_downloadhelper-7.6.1a2-an+fx.xpi 2021-07-05 19:31:12.868635411 +0200
video_downloadhelper-7.6.3a1-an+fx.xpi 2021-09-06 16:46:15.031752425 +0200
video_downloadhelper-7.6.3a2-an+fx.xpi 2022-06-14 11:56:58.855151925 +0200
video_downloadhelper-7.6.3a3-an+fx.xpi 2022-06-17 10:56:23.845434552 +0200
video_downloadhelper-7.6.3a4-an+fx.xpi 2022-07-05 18:05:55.312489777 +0200
video_downloadhelper-7.6.3a5-an+fx.xpi 2022-08-01 15:55:32.570693981 +0200
video_downloadhelper-7.6.3a6.xpi 2022-08-16 16:46:42.045502721 +0200
video_downloadhelper-7.6.5a1.xpi 2022-12-03 17:15:45.551071459 +0100
video_downloadhelper-7.6.5a2.xpi 2022-12-03 17:35:43.856032142 +0100
video_downloadhelper-7.6.5a3.xpi 2022-12-03 18:40:52.060874912 +0100
video_downloadhelper-7.7.0a1.xpi 2023-06-23 01:20:41.098120244 +0200
video_downloadhelper-7.7.0a2.xpi 2023-07-03 16:25:42.276370433 +0200
video_downloadhelper-7.7.0a3.xpi 2023-07-05 17:20:31.398646302 +0200
video_downloadhelper-7.7.0a4.xpi 2023-07-06 17:00:39.308201903 +0200
video_downloadhelper-8.0.0.0a2.xpi 2023-07-07 14:55:42.662514487 +0200