Once SDL contract is over, what happens to the current running site in
production? Will that stop working?
Yes (if the question tags are correct). But, even if it continues running, having it that way would be using unlicensed software which has legal implications. Contact SDL (RWS) directly to see what your options are.
See also Nuno's comment below. ...
Yes, as Nuno mentioned in his comment, Core Service can be used. And if you ask me, I'll probably use it. Another option, if you plan on just clicking is using Content Porter.
It can export all items with their references, and you can import them into another Tridion Environment. You can also check the packages it creates. They are self-explanatory with a ...
All the content is in the database. Backup your database, there's your backup.
As for migration, good luck. Blueprinting and content relationships will probably make your life miserable while writing the scripts. CoreService is your friend, I guess.
FYI - And this applies to all migrations. If your content structure is wrong to start with, it will be wrong ...
The first issue clearly states that the custom models and views have not been registered with DXA. You'd have to create a class that extends AbstractModuleInitializer and register all views and custom entity models. For your setup you should have something like this:
public class ...