socket over footer or widget on 2 row with 1st column as full width section

Hi I would like to know if you could help me with applying a call to action bar just over the footer without altering the template files, so only with function.php and css

I tough about 2 way to make it but they may not work or there might be other way

1) use the socket and display it just before the footer section. That could really work, but really dont know about the css to make it

2) Found information about using the 1st or last column to make it a full row and worked from there to end up with this code

#footer .flex_column:nth-child(1) {
    width: 100%;
    margin: 0;
    background-color: #3f3f3f;
}
#footer .flex_column {
    width: 27%;
}
#footer {
    padding: 0px 0 30px 0;
}

From this, I would like to get the content back to container position cause for now it’s like left align. Also my 1st column is not taking it all width in small display

Thanks for helping with this