Thanks for sharing the image!
1. "I was confused about the graph top of the y-axis, this is a line chart or an AreaRange chart?" - as you can see in this demo: https://jsfiddle.net/BlackLabel/bsnt9Lw0/
the last series:
- has 2 custom markers
- stretches from (x = 2, y = 2) to (x = 8, y = 2)
- has a line width of 20
- is of type spline
You can check all the options available for the spline series here: https://api.highcharts.com/highcharts/series.spline
2. "I wanto to show the line between the two rows and need to show the markers" - isn't that exactly what you sent me in your initial post? This demo has a spline series (as I've described above) which achieves exactly this result.
Could you please specify what can I help you with? From what I see, you've already managed to add this "line" with "custom markers".