Apple has a number of "very serious" issues under the European Union's sweeping rules aimed at reining in Big Tech, the bloc's competition chief Margrethe Vestager told CNBC on Tuesday, following reports that regulators are preparing charges against the iPhone maker.In March, the European Commission, the EU's executive arm, opened a probe into Apple, Alphabet and Meta, under the sweeping Digital Markets Act (DMA) tech legislation that became applicable this year.The investigation featured severa...