wphigh

this is not required. It is just add different class at different IE version. then you can fix IE bug via class.
For instance:
.ie7 .post { ... } will only affect ie7
see twentyfourteen\css\ie.css

access sidebar.php file to clear code. Or sidebar-right.php, sidebar-left.php, etc. But remove sidebar perhaps theme layout will incorrect, fix it via css.

<!--[if IE 7]>...<![endif]-->is a conditional statement only support IE 9-.
see https://en.wikipedia.org/wiki/Conditional_comment

It’s difficulty if you are not a developer. You can install plugin Slim Jetpack

function html5wp_excerpt() is used to display post excerpt. So replace it width the_content(), or access functions.php line:234 to modify html5wp_excerpt().
see: https://github.com/toddmotto/html5blank/blob/master/functions.php

See: https://github.com/toddmotto/html5blank/blob/master/loop.php

Line 26: <?php html5wp_excerpt('html5wp_index'); // Build your custom callback length in functions.php ?>

change to:
<?php the_content(); ?>

What is the theme download link?

Use chrome and try again.

See: Resetting Your Password

try:<table style="width: 100%; table-layout: fixed;">

See your approved plugin email details from WordPress official.Using TortoiseSVN software to update. download: TortoiseSVN

You can custom css to change this background color, see here

see this example:https://jsfiddle.net/FJ6wX/21/

access phpMyAdmin via your site server. wp_users table show all of user’s name and email.