Is there a workout to undo the changes if you are not the admin and mistype the <accesscontrol> tag?
Topic on Extension talk:AccessControl
in fact the help here is very useful (and readable after translating to English with google) [https://www.thewoodcraft.org/wiki/index.php/AccessControl]
When you can't get to the page
Do not panic!
If you mistakenly removed your name from the list of users authorized to edit the page and you know another user who has access to edit the page, you can try to ask the user to correct your mistake and add you to the list again.
If you do not know anybody and no other user has access to the page, you must ask for help from a user who has administrator rights ('sysop').
However, this will not help if the privileged status of this user group is disabled via $ wgAdminCanReadAll , or if you have managed to block access to a page in such a way that even an administrator (a user in the 'sysop' group) cannot access it. Such a situation may occur, for example, in the case of multiple translucency.
Then you have only one option.
If you do not have access to the configuration file LocalSettings.php, you must ask whoever has access to temporarily deactivate AccessControl so that you can fix the faulty record, or to fix it for you - the easiest and quickest thing is to completely delete the page content. You can then draw it from a previous revision and it will minimize the time it takes to solve your problem.
A little workaround which may also make editing faster: Create a template "Accescontrol" and add the content to go with the tags via an unnamed parameter. Have not tested this but it should work. But yes, a mistyped tag should probably not result into something like this.