1- To get a list of authors, you can use:
<?php wp_list_authors( ); ?>
This will return a list of authors and a link to their accounts and posts. To customize it using your desired arguments, take a look at Codex
2- To retrieve the categories, use:
<?php wp_list_categories(); ?>
This function will return a list of all categories as an HTML list. You can customize this too, here.
3- Finally, to filter the posts by date, you can use the method suggested in the link you provided, by using:
<?php wp_get_archives(); ?> and setting the arguments to monthly, or yearly. The guide has explained it pretty well.
Note: You don’t need to use <options> selectors to make a drop down menu. These functions will return their results as HTML list, so you can style it just like a drop down menu. A full guide about CSS drop downs can be found here.
Tell me if you need more details on any of these.