TED HESSON, MIMI DWYER, MICA ROSENBERG and KRISTINA COOKE U.S. President Joe Biden has signed half a dozen executive orders to reverse several hardline immigration policies put in place by former President Donald Trump, although migration experts warn that it will take months or longer to unravel many of the restrictions imposed in the past four years.  In a sharp departure from his Republican predecessor, Biden, a Democrat, just hours after being sworn in, also sent an immigration bill to Congress that proposes opening a path to citizenship for millions of immigrants living in the United States unlawfully. The executive…