limit Highcharts x-Axis grouped categories and labels style - css

Question

I am trying to draw a chart as below but the x axis stops at end of year 11 which it does not at the moment. I set max to 19 but it did not work.How can I get rid of those grey lines after end of Year 11?
Also for x-axis labels I want to decrease the font size of second category ([1,2,3,4]) and Year with bigger font but in label styles the font size property applies to all labels.
var l=19;
var m=-0.6;
new Highcharts.Chart({
chart: {
renderTo: elementId,
spacingLeft: 10,
spacingRight: 10
},
title: {
text: subject
},
xAxis: {
categories: [{
name: "Year 7",
categories: [1, 2, 3, 4]
}, {
name: "Year 8",
categories: [1, 2, 3, 4]
}, {
name: "Year 9",
categories: [1, 2, 3, 4]
}, {
name: "Year 10",
categories: [1, 2, 3, 4]
}, {
name: "Year 11",
categories: [1, 2, 3, 4]
}],
labels: {
style: {
fontSize: '7.5px'
}
},
plotLines: [{
color: '#5DA06E',
width: 2,
value: l
}, {
color: '#5DA06E',
width: 2,
value: -1
}],
//max: l
},
yAxis: [{
labels: {
enabled: false
},
title: {
text: null
},
min: 0,
max: 1000
},
{
title: {
text: null
},
labels: {
style: {
fontSize: '7.5 px'
},
align: 'left',
x: 3,
formatter: function () {
var value = change[this.value];
return value !== 'undefined' ? value : this.value;
}
},
tickPositions: [0, 280, 360, 440, 520, 600, 680, 760, 840, 920, 1000],
gridLineColor: 'white',
opposite: true,
min: 0,
max: 1000
}],
series: [{
type: 'line',
data: [[m, 0], [l, 280]],
color: '#A5DEC1',
}, {
type: 'line',
data: [[m, 80], [l, 360]],
color: '#94D0A3',
},
...
strong text

Answer 1

Are m and l params constant? Or can you change them? If yes, then see: http://jsfiddle.net/TFhd7/373/
In short: Categories reserves a place from -0.5 to 0.5 with category index. For example Year7 -> 4 means x-values from 3.5 to 4.5. So according to this information let's change that values:
var l = 19.5;
var m = -0.5;
Now modify extremes and plotLines:
plotLines: [{
color: '#5DA06E',
width: 2,
value: l
}, {
color: '#5DA06E',
width: 2,
value: m
}],
max: l - 0.5,
min: m + 0.5,