even if the wing doesnt pass the rules you can do whatever you like in practice sessions ?
You can run what you like in testing, which at the moment is pre season only. Anything you run on a race weekend, in any session, needs to pass the FIA tests.
Wether they invent new rules or ban things on 'safety grounds' after you have run them on a Friday, is up to them (the BMW wings at Canada a few years back, for example)
It's been brought up many times, but since they used video evidence to ban flexy rear wings (IIRC), why can't they do the same for front wings..
They used video evidence to show there might be a problem, then changed the rear wing stress tests to test for it.
Exactly what they have done with the front wings. The RBR was shown to flex, the FIA changed the test, the RBR wing still passed.
Its legal.