Seems like there is an issue with the cached dictionary file maybe. Try deleting dictionary.dat file from the website/temp folder and clearing the cache if necessary. Any reason you are using TextByLanguage() eather than Sitecore.Globalization.Translate.Text("key") and letting that do it's fallback thing?

If you really struggle and don't actually need things to be published, you should consider just switching to using the master database directly. There is a LiveMode.config example you can use as a start.

So you now NEED to be associated with a partner, just being certified is not enough? What about those working for end clients directly or freelancers who are not associated to a partner?

If you are using Docker, would it not be better to create a custom image and do whatever post setup stuff you need in that? You will probably be tearing down/up the instance many many times during development...

Seems kind of counter-intuitive to go the effort of creating a button in C# and then not just writing the code in C#....

Someone selected the "Upload as File" option, it's a checkbox on the "Advanced Upload" dialog.

I am going to assume with Approach 3 above you manually edited the hosts file with your Docker IP address, and it is still running under http, you did not bind an SSL cert to it? You need your instance to be running using https so you need to add bind your cert...

This is likely a caching issue, either directly on the forms wrapper component or a parent component. You can verify by disabling caching and checking again.

If you are running youe code against the master database and have no access to Context, then you could use Sitecore.Configuration.Factory.GetDatabase("master")