PPL/IR/CPL XC req. landing at least 50NM away.
135 - IFR mins req 500 hrs XC which may include any landing at a different airport regardless of distance.
ATP - 500 hrs XC req. at least 50NM but no landing required.
Example: fly an Instrument approach at an airport 35NM away but the IAF is 50NM you may log it as XC for your ATP. However, in the comment section you need to document the waypoint.
If you landed out of this approach you could count it for 135.