Use select2() function on select element to convert it to Select 2.

Add options inside the optgroups to for group options.

Apply Placeholder by setting option placeholder option.

Set tags: true to convert select 2 in Tag mode.

Use data('select2') function to get container of select2.

Disable Select using disabled attribute.

Set maximumSelectionLength: 2 with tags: true to limit selectin in Tag mode.