Regarding POKEY audio, most homebrews expect to address the chip at $450, which has become the defacto standard. The old Prosystem emulator only supports POKEY at $4000, as implemented with the Ballblazer cart.  Games that support TIA or POKEY and try to detect a physical POKEY will likely fail due to inaccurate emulation.  I remember looking at the Froggie code years ago and it would write to POKEY at both $450 and $4000, which is probably why it works, though the bad notes indicate the POKEY e