Is it possible to have the last stage (finish location) blocked that it only can played as the last stage?
There are several ways this could be done, here are two suggestions:
With the help of an Outro
Under the setting Sequence of stages you will find the option to set an intro or Outro.
The Outro is displayed after all other sections have ended or after clicking on End Bound.
However, an Outro can only be set for flexible or random Sequence of stages.
More information here: Sequence of stages
To do this, you activate switches for your bound and create a section at the end with a condition that only triggers if an element or section before has been solved or reached.
More information here: Switches
I hope this helps you with the creation of your Bound.