Can I change the theme name in WordPress?

All the above is correct, but is not enough. After you rename the theme, e.g. rename the folder old-theme --> new-theme, you should copy the theme customizations (colors, header / footer, widgets, etc.) from the old theme to the new theme. This is done directly in the MySQL database:

1. Find an option named theme_mods_old-theme in the table wp_options
2. Copy the option_value (it is a text holding the theme customizations in a special WordPress format)
3. Put the copied value in a new option named theme_mods_new-theme in the wp_options table.

Step 1: Firstly go to wp-content/themes/ folder. And then rename your theme folder to whatever you want.

Step 2: Open your theme folder and open style.css file. In top part of style.css you will see theme name. Rename it and save changes.

Step 3: Go to Wp-admin/appearance/themes and activate your theme under new name.

If you are using child/parent theme and you also rename parent theme folder&name, so after Step 3 you should additionally change parent theme path (template field) in child theme’s style.css.

note : renaming your theme will stop its automatic updates, you should do it manually in the future.

You can absolutely change the name of the folder without having any problems. If you want to change just the themes name, open the style.css in the root folder of your theme and edit the name in the comments at the top of the file. If you plan on doing more changes, you might be better off creating a child theme: https://codex.wordpress.org/Child_Themes