Keeping track of the suction & discharge lines can be a little tricky. Four lines meet at the reversing valves: one up and three down. That's why the reversing valves are also called four-way valves.
When you can identify a normal discharge line and a normal suction line, it becomes easier to keep track of them.
Normal discharge and suction lines shall always be used for either discharge or exclusively suction. They do not change their function regardless of the mode of operation. The normal discharge line always runs from the compressor to the side of the valve.
It is usually at the top but not always. The common suction lines are the middle line at the bottom of the reversing valve. No matter what the operating mode, the suction line will always lead to the compressor. The two lines next to the normal suction line can switch between discharge & suction.
Their functions depend on how the reversing valve routes the refrigerants. Canoes loop the suction line back to any of the surrounding lines. Check out the bottom line of blue arrows in the image below to see it in action. Systems are in the cooling mode because the pressure differential is on the right.