How Do I edit the Side bar widget separately from the footer widget

Hi there,

Try this for underline widget title:

.sidebar h2.widget-title {
    text-decoration: underline;
    text-decoration-color: yellow;
}

I'm not sure what you are referring to #2 and #3. Can you explain a bit?

Let me know :)

I have taken care of #3 and #4.

Please also include CSS to adjust the line colour and thickness. Thank you

We would need to use border property instead of text-decoration:

.sidebar h2.widget-title {
    border-bottom: 2px solid #000;
    display: inline-block;
}