FreezeWP - Code Freeze Your WordPress Dashboard

This plugin was developed to aid multi-user sites when they are being moved from one web host to another. In this case, the following workflow may be helpful:

• Download a backup of your site (cPanel, etc.) and database. (Export and backup options are still available even if this plugin is already active.)
• Install the FreezeWP plugin on the old site, and activate it. This will alert others that content changes won't be accepted or will be lost.
• Upload/import your old site to your new one, and don't install the FreezeWP plugin there (unless you want to verify everything before returning the site to normal).
• Notify your users that when the "FreezeWP" message is removed, they may resume their work. When DNS changes are in effect, you'll be directed to the site that doesn't have it installed, and all should be well.

Just deactivate or delete the plugin. There are no changes made to the site or database nor any settings to worry about.

Not exactly. Many of the restrictions are hidden options rather than disabled capabilities, to reduce complexity. Therefore this is not intended to be a 100% bulletproof solution to preventing changes to your site, as a user who is familiar with the URL syntax of the different commands may still make changes. Additionally, some plugins may continue to expose options that can be modified, though this should be rare. While not completely bulletproof in every circumstance, it is designed to keep the average user from making changes during a brief time frame (such as waiting for DNS changes to take effect).

Edit the values in the appropriate language file. If there isn't one for your locale, go ahead and create one.

Yes. The plugin can be network activated rendering all sites on the network effectively read-only. However, it does not support loading via the mu-plugins folder at this time.

Let me know what you discover is still available and I'll try to disable modifications to it where appropriate.