Please update to WordPress version 4.7

Click the above link to the WordPress Codex regarding WordPress 4.7 For Developers.

Page Templates for Post Types Add support for post type templates.

Add support for post type templates. By opening up the page template functionality to all post types, theme developers have even more flexibility with the WordPress template hierarchy (read more).

If you would like all Post Types to have template selection functionality, please update to WordPress version 4.7.

Quoted from the codex page linked above:

Page Templates for Post Types Add support for post type templates.

Add support for post type templates. By opening up the page template functionality to all post types, theme developers have even more flexibility with the WordPress template hierarchy (read more).

As far as having custom template for other areas of your WordPress website; Please refer to the following useful links:

1. Developers :: Theme Handbook OR Codex :: Theme Development
2. Developers :: Theme Handbook :: Theme Basics :: Template Files OR Codex :: Templates
3. Developers :: Theme Handbook :: Theme Basics :: Template Files :: Template Files Section