Whilst legally correct, it's ethically dubious, although I'm not 100% sure what the OP intended.
That's more a feature of the USA, not Europe. In the UK, at least, you can return any item within 14 days in its original condition if ordered mail order, no restocking fee, and you have very good policies for returning items (or having a repair) for those with defects.
Apart from needing a setup (which was not attempted) I'm hard pressed to see any show partucular stoppers, given the information provided. The knob issue was particularly silly. If the truss rod lacks adjustability its another issue, but currently an unknown.