rebuild a foot

It's going to take some time. The workflow is pretty much as I described. Here's a project file that gives you the basic steps. All that is left is to finish the puppet pin morph in the nested comp, animate the mask in the main comp, then finalize with some color correction. It would probably take me two or three hours to finish the project. When you do the work you need to be working with the original files. You want as much detail as you can possibly get.

Step 1: Trim the footage, create a new comp, resize the comp, duplicate the footage, set markers for the last good frame and the first good frame, freeze-frame the layers, mask the foot.

Step 2: in the Morphed comp start with the last good frame and animate the puppet pin moving the repaired foot as close as you can to the guide layer original footage. When the first frame layer has gone about as far as you can go because of the shape of the foot and the lighting changes turn off the layer and start on the first good frame layer beginning at the out point. When the layers meet, overlap, and do a crossfade. You won't get perfect edges and blends yet, but get as close as you can to a realistic-looking foot.

Step 3: back in the main comp animate a soft edge mask to hide as many imperfections as you can, then apply color correction.

Like I said, this is going to take a while but you should be able to get something that is usable. 

This should get you started. 

Put the original footage on the bottom layer, duplicate the footage layer and move to the last frame where the dancer's foot goes out of frame. At that point either use the Composition/Save Frame As/Photoshop Layers menu or use Layer/Time/Freeze Frame (if the foot only moves out of the frame once). Now you are set to start the masking process. If you have multiple times when the foot moves out of the frame you need a new PSD of the last good frame each time. If the foot only goes out of frame once you can use a freeze-frame. 

The next step is to create a mask for the foot. It is easy in Photoshop, and fairly easy in After Effects. You will want to add some feathering around the heel. If you set the anchor point of the layer on the center of the heel it is going to be easier to match things up. 

Trim the layer so that it is only long enough to cover the part where the foot is out of the frame. Mask the foot as shown and add some feathering below the heel. Animate the position and rotation to match up the movement as close as possible. You will probably need to add Puppet Pin to deform the foot slightly as it moves up and then back down. If needed fade out the last two frames when the toes come back into the frame. You want the replacement foot as small as necessary yet big enough to give you something to match up with the rest of the foot. In this screenshot, taken from your sample images it took 6 puppet pins to match up the foot so there was no visible shift in the size or look of the foot. 

I hope this gets you started.

You'll need to duplicate the dancer footage, motion stabilized the so it doesn't move when it is in the frame, probably freeze-frame, then generate or draw a mask for the foot, then motion track the original and whenever the foot goes out of frame, you will use the duplicate layer. 

Are you new to AE? Do you need more explanation that that?