Error installing Tabs and Accordion

Please read the documentation carefully on how the syntax works:
docs4.regularlabs.com/tabsaccordions/get...started/introduction
docs4.regularlabs.com/tabsaccordions/the...s/default-opened-tab

PS: the issue you are having with the autoload_psr4.php file is exactly the same as we concluded last year:
regularlabs.com/forum/bugreports/51116-f...ing-to-10-0-4#110969