Private app limit

I’m thinking in an app in which different groups of people can be in different meetings. I need only the functionality to join a meeting with the meeting data anonymously. I don’t need any of the functionality of a signed user, then I do not need neither the oauth mechanism.
To do this, I only need to initialize the SDK (using only the SDK credentials to generate the JWT) in a private app and I have no to publish it.
I’m not sure if what I’m thinking could be possible: I have some doubts:

1.- Does this mechanism of initing the SDK using a JWT be valid after 2023 June?

2.- How much time can a private app live in the zoom’s marketplace without publishing it?

3.- Has a private app some type of limitation in for example how many users at the same time can use the app to join to a different meetings in groups?

If somebody of zoom can answer me, I’ll appreciate it.