Hi. How to make custom k2 tag page with modules and custom content. How to display items by tag anywhere in this page? Can this be implemented? Thx in advance!

By default tags are rendered in the tag.php file. If you want different modules per tag you need to assign these tags to a menu item (K2 Tag Menu item).

If you want to have a different template per tag/ menu item you can create a new K2 template and c/p tag.php in that folder. Finally you need to select that template from the menu item's settings.