Create a native SDK using Flutter

Question

I'm with a task but I don't know how to start this I searched a lot, there are very few articles about that, but none of then worked

I need to create a SDK (library aar, framework) in flutter to be used on native code

If you guys can help me with this 3 points I'm sure I can continue and implement all that I need

1. What I should create to be able to link a Flutter SDK in native code ? Should it be a module, a plugin or a ffi-plugin ?
2. On the flutter SDK how can I ask for a token and follow start a flutter screen inside the native host application ?
3. How should I do on the host application to import the SDK made on flutter and interact with it ?

If anyone could me help with this I will really really be grateful