You can uninstall B2B Handsfree like any other Shopify app by going to Settings > Apps and sales channels in your Shop's admin and clicking the ... next to the app and then Uninstall to delete the app.
After the app is removed from your store, you may want to delete the custom registration form and page that might have been created. To do this, please follow these steps:
Go to Online Store -> Pages in your store's admin.
Click the checkbox next to the page named Register (B2B). If you changed the name if this page, select the appropriate page.
From the Actions dropdown menu select Delete pages and confirm the deletion of the page.
Go to Online Store -> Themes, click the Actions dropdown menu next to the active theme and then click Edit code.
In the code editor, find a file named page.b2bapp.liquid or, if you're using an OS 2.0 theme, page.b2bapp.json, in the templates folder.
Select the file in the editor's file list and click the trash can icon next to the file to delete it.