I live in a hilly area and want a drivetrain with 50/34 crankset and a 10-42 cassette. Can I use a 2x front crank with a 1x rear derailleur?

1x rear derailleurs are either Road or MTB specific. They will not work with any front shifting system- the derailleur will not move in a way that allows for chain movement between front chainrings, as it moves on one axis only- we call this X-HORIZON™. The X-HORIZON™ rear derailleur’s ‘straight parallelogram’ design limits all movement to the horizontal axis, which makes ghost shifting impossible while also reducing shift force. For quicker, more exact shifting, the large upper pulley offset design maintains a constant chain gap across all gears. X-HORIZON™ rear derailleurs will not work with a front shifting 2x or 3x system.