ACE-DL has a rewind feature, but it is not as good as it could be: [https://youtu.be/wIKGvpnJLUo Demonstration of rewind in ACE-DL]
At the moment, only the RetroArch CPC emulator has a proper rewind feature like those in games such as "Prince of Persia: Sands of Time" or "Braid" for PCs: [https://youtu.be/YwilYlSe5LQ Demonstration of rewind in RetroArch]
A very simple approach would be to make a SNA for each frame and limit the RAM snapshot to 128KB, which is ok for 99% of CPC software.