Whether the bankruptcy declared on 2011-04-12 had to be annulled after the concordat was homologated and executed.
Yes. The homologation of the concordat extinguished the prior enforcement proceedings, so the non-final bankruptcy was annulled retroactively as of 2013-07-12.
Under Art. 311 LP, homologation of the concordat extinguishes prior enforcement proceedings except pledge realisation. Since the bankruptcy stemmed from that enforcement, it fell away once the concordat was homologated and executed.