Radek Mezulanik

This plugin generates unique codes and creating custom field in user profile called <code>Ref code</code>. 
You can enable access gate, to allow users to access website only with their unique ref code. 
Access gate is just post with shortcode inside, so you can create whatever text/design you want.

Zedna Ref Code Generator & Access Gate

Generate unique code for users to allow them to access your website.

Plugin works automatically. When activated, it duplicates all the widgets to new WordPress websites in your multisite network.

Zedna Multisite Sidebar Widget Duplicator

Create a duplicate of all widgets in master site for each newly created sub-site.

Zedna Ref Code Generator & Access Gate vs Zedna Multisite Sidebar Widget Duplicator