The below code opens the first tab on load.
var accordion_head = $('.accordion > li > a'),
accordion_body = $('.accordion li > .sub-menu');
// Open the first tab on load
accordion_head.first().addClass('active').next().slideDown('normal');
How can I open a tab by name/id or position on the list (e.g. the 4th item)?
You can open 4th item like:
accordion_head.eq(3).addClass('active').next().slideDown('normal');