Is back button a breadcrumb?
The back button is unnecessary
The point of the breadcrumbs is reduce the number of actions a user needs to take in order to get to a higher-level page. Therefore, breadcrumbs provide detailed back button functionality because users can go back to any previous navigation level.
When should you not use breadcrumbs?
Breadcrumbs aren't necessary (or useful) for sites with flat hierarchies that are only 1 or 2 levels deep, or sites that are linear in structure.
Should breadcrumbs be clickable?
They help site visitors understand and navigate your website's hierarchy. A location-based breadcrumb trail should begin with a link to the website's home page and end with the current page. The last item in the breadcrumb trail should not be a clickable or tappable link.