Development Mode allows you to temporarily suspend Cloudflare’s edge caching and minification features. The expiration period for Development Mode is 3 hours. 

Development mode is useful if you are making changes to cacheable content (like images, css, or JavaScript). It would like to see those changes right away.

You will find the Development Mode option by selecting the ‘Caching’ option from the top bar menu:

Development Mode will be find at the bottom of the page:

NOTE: Development Mode does not clear the edge cache for your site .It simply to suspends the use it while Development Mode is enable. If you need to specifically clear the cache you should use the Single File Purge or Full Cache Purge functions.