Downgrade joomla 3.8.7 to 3.7.5 pls report and fix

[2dmaster]

Downgrade joomla 3.8.7 to 3.7.5 not work only one fatal error

PHP Fatal error:  Class 'Joomla\\CMS\\Plugin\\CMSPlugin' not found in /public_html/plugins/system/sessiongc/sessiongc.php on line 23

pls report and fix ! important

when upgrade 3.2 to joomla 3.8.7 i get error

PHP Fatal error:  Call to undefined method JVersion::isInDevelopmentState() in /administrator/includes/framework.php on line 30

upgrade trash to joomla 3.8.10

PHP Fatal error:  Maximum execution time of 30 seconds exceeded in /public_html/test/libraries/joomla/log/entry.php on line 103
PHP Notice:  Constant _QQ_ already defined in /public_html/test/libraries/src/Language/Language.php on line 18

3.8.10 to 3.4.0 - update package
JHtmlBehavior::polyfill not found.  at /installation/index.php

HP Warning:  fclose() expects parameter 1 to be resource, boolean given in /plugins/system/yt/includes/libs/minify/lib/Minify/Cache/File.php on line 104, 101,102,103


we have 3 popular errors and now we cannot upgrade/downgrade joomla anymore >> pls report and upgrade

[jenkinhill]

WTF has this got to do with VirtueMart? And please don't shout.

[Studio 42]

No backups ?
You should try a full install package, some files are not included on update/downgrade.