By Pavel Polityuk LVIV, Ukraine (Reuters) – Ukraine’s president has not altered his stance that his country’s borders must be recognised as the frontiers it had at the time of the Soviet Union’s collapse in 1991, an aide said on Thursday. The comments by political adviser Oleksiy Arestovych appeared designed to douse any talk of President Volodymyr Zelenskiy allowing border changes to secure a deal with Russia to end its invasion of its neighbour. Russia annexed the Crimea peninsula from Ukraine in 2014 and Russia has recognised declarations of independence by the self-proclaimed republics of …