Answer 1

I can see you edited your code, please don't do that😅
Now at line 20 you are going to need this too
return this.unsubscribe.bind(this);

By the way, what you are doing is really cool and a great way of learning.

Answer 2

At line 24 you have:
return [s.dispatch,s.getState, s.subscribe]

The "this" context is lost when extracting methods that way, see my full explanation below:
https://www.sololearn.com/discuss/2527815/?ref=app

So this is one of the possible fixes:
return [s.dispatch.bind(s), s.getState.bind(s), s.subscribe.bind(s)]