Yes, you can always choose any hypothesis you want. It's largely irrelevant.
Every experiment will support analysis through a set of hypotheses. Just because you didn't select all of those hypotheses before the experiment ran doesn't mean you can't select it after the experiment.
Imagine that an experiment has been run, but you do not know the results (or even what was done). Now you select a hypothesis, if the experiment required to validate the hypothesis is the same as what was run previously, you can now look at and use the results.
A hypothesis is like running a query against a database. Many queries are valid, even though the data may not have changed.
>Otherwise, why are you re-running it?
Science requires it. Doctrine from one-off experimentation is religion (hard to dump).
Are you claiming that this statement is untrue, or irrelevant?
> Besides, you would always run a new experiment again anyway.
Then surely the initial experiment doesn't count. Otherwise, why are you re-running it?