I've learned two versions of a capella songs, so I think playing may follow the same lines.

I spend time listening to the "newer" version & singing along until I can do it by rote. I then pick a memorable phrase with a unique sound that I use as my cue to pick out the tune, since I don't use sheet music when I sing. I hope this is clear.

Singing & playing both use body memory to set yourself up for a song, so you need to learn two separate cues for two different versions... otherwise you never can be certain which one will come out...lol.

After you master the newer version, then you try switching back to the first. You should be able to switch between versions after a bit of practice. good luck!