[Solved]-HighCharts Line Chart draw y axis line for entire line points and only one line-Highcharts

You can add a dummy column series with the same data as spline to create those lines.

{
    type: 'column',
    data: [49.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4, 194.1, 95.6, 54.4],
    showInLegend: false,
    enableMouseTracking: false,
    states: {
      inactive: {
        opacity: 1
      }
    },
    pointWidth: 1,
    color: 'rgb(230, 230, 230)'
  }

Demo: https://jsfiddle.net/BlackLabel/tfqrv296/