It was not sanctioned by the state so not a referendum just a regional vote to show opinion. Would the result be the same IF the result was binding, probably not.
The result should be used for indication only and a bargaining chip for the Catalan Government to lower tax payments to Madrid.
No Idea.....
You would need to look at the constitution. There may be secessionist clauses that make the attempt to organise people to want to leave the 'federation' to be illegal. A populist vote could be such a move. So could be illegal but that is for the prosecutors / courts to decide....
I think a referendum of this importance can only be held at the National level.
Under Spain's Constitution a region "cannot unilaterally call a referendum on self-determination to decide on its integration in Spain", according to a written summary of the ruling released by the Constitutional Court.
If Catelans become independent Spain will have no soccer team without Barca
players remaining as Spaniards