Sorry for the wait, I was waiting on an answer. I have been told that it is not a possibility to add the other strains. They said that it was a bug in the first place that users were able to stop on the earlier stages, so it really wasn't supposed to be possible. If you claim now, you will receive the skin for the final strain.

I don't think that you HAVE to turn it in but I may be wrong. BUT it may be that some newer features (like the no cutout BGs) may not work for you since you may not be able to move that base.

You are welcome! I am going to go ahead and close this up since the strain will not be unlockable.