How to? - Character with feet facing backward (walk cycle )?

You say you don't have much time... so I only have suggests for experiments, which might not be useful.

Could you share a screenshot showing the handles you have on the feet?  e.g. are you using the toe handle etc.

One idea is to try and trick the software into the shape of your feet. Eg add a normal shoe/foot to the character then make that layer invisible. Put the normal walk tags on that. Then the visible foot is effectively just decoration sticking out the back of what ch thinks is the foot. It will hopefully leave that alone since ch thinks it knows what your foot is.

Another idea. Draw a leg from the knee of the real leg to the toe sticking out backwards. Rig that layer as if it is the real leg, but hide it. Put a handle for the heel/ankle where the toe is visually. The heel you can see is then marked as the toe. The idea is to try and tag the foot backwards, then use a fake hidden leg again to trick ch into the structure that you want rather than what it wants.

No idea if it will work, but that is my idea. Make sure ch either does not think your foot artwork is part of the foot it should be warping etc for walking, or make it think the foot is backwards by adding a hidden fake leg. No idea if it will work...