Even if the storefront is closed (the status set to OFF), you'll be able to view it if you have an access key. Go to <a target="blank" href="[url]">Settings → General</a> and specify the <i>Access key to temporarily closed store</i> setting. Please note that a different key can be specified for each storefront, so make sure to select the correct storefront first. Use the key as described in the tooltip of that setting.