Hello!
As there is no place to review the complete specialization, I'll do it at this place.
I general I think I learned a lot and have now a good foundation of RL.
But on the other side IMHO there is the need for some improvements:
1. Questions get not answered at all: I asked some questions through the course and did not get an answer to one of them.
2. The textbook you provided does not fit to the way I'm learning: much too much text and not enough (mathematical) proves. It would be good to have alternative readings here.
3. Some of the tests in the assignments are not ok: they leave you in the impression that everything is fine - until at some point later there is the need to review everything. This is IMHO a waste of time - a test should test all (or at least) the most possibilities.
4. I'm missing something like course no 5. All the details are now introduced - and now the 'real work' on a architectural and conceptual level can start. But there is nothing like this.
5. It would be good to generally update the python assignments that they work with the lastest versions of their dependencies. The problem is that with the current setup it is mostly impossible to develop and execute the assignments locally. (e.g. gym 0.21 might be updated to the latest gymnasium, in one assignment even the random number generator does not fit, that the local version failed but the online succeeded (IMHO the concept relying on the same random numbers is a bit brittle, might fail and introduced a lot of questions and work))
6. Please use environments like tensorflow for handling NN. As I understood, this is not an introduction to NN - so just use what is there (there is no need to develop (again) an Adam optimizer - it does not really help to understand RL.