
Yebng |

"Shapechanger (Su): At 1st level, a metamorph gains
the ability to transform herself into another form. This
ability functions like alter self, except as noted here. The
effect lasts for 1 hour per metamorph’s alchemist level, or
until she changes back. Changing form (to another form
or back) is a standard action that doesn’t provoke attacks of
opportunity. The metamorph is fatigued for 1 round each
time she changes shape."
The above bolded area is where I'm seeking clarification. Does it imply that I can change from one shape to another without reverting to my original shape? and will it cost me an additional use of the ability to do so since it specifically says the effect lasts until you "change back"?
I lean towards yes and yes, but I can see an argument for yes and no since you never "changed back".

Yaba |

Unless the ability text specifically says that you can change shape multiple times with a single use of the ability, each new assumed form requires another use of the ability. As far as needing to change back to natural form between assumed forms, I agree that it is not required. As long as the ability to assume forms comes from a class feature, the option to do so remains available regardless of the character's current form. Beyond that, the behavior would comply with standard rules for resolving the effects of two similar (or identical) non-stacking spells cast on the same target.