You should be working in a local development environment and then deploying the changes to production once ready, not creating a development theme and trying to make it only accessible to you in production.
For this, you'll want to use a version control system like Git. There are many hosted versions around like bitbucket, github and gitlab. This will help you keep track of your changes. Once you're ready you can the deploy the changes to live, e.g. with deployhq.com
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