Config changes
App Versioning
There are two files that get copied to config.xml when building - config_BoldNetMobile.xml (contains config settings for the BoldNet Mobile app) and config_legacysecurity.xml (contains config settings for the Legacy Mobile app). When you build, one of these files overwrites config.xml so you'll want to make changes in the config_BoldNetMobile.xml and config_legacysecurity.xml files instead of in config.xml.
There are certain things you need to change in the config files for each build you intend to put in the app stores - even if it's just for testing.
android-versionCode is an internal version number for Android. If you don't increment that, Google Play will tell you that the version already exists.
ios-CFBundleVersion is the same thing but for Apple - an internal version number. Apple's app store will tell you that the version already exists if you don't increment it.
version is the visible version in the app store for both stores. We usually only change this when we're going to push a new app to the app stores.
Important! Make sure you edit config_BoldNetMobile.xml and config_legacysecurity.xml.
Plugins
We want to keep our plugins up to date for security reasons. I suggest finding the latest version of each plugin and upping the version number to match it. If you load package.json, go to the beginning of the version number, hit ctrl+space, it will show you all the versions for the plugin.

"cordova-android" and "cordova-ios" are only found in package.json. These are the versions of cordova the apps will use. If they get too far out of date the app stores won't accept new app uploads.
Plugins in config_BoldNetMobile.xml and config_legacysecurity.xml:

Make sure you edit the version numbers (if necessary) in package.json as well as config_BoldNetMobile.xml and config_legacysecurity.xml.
OS Versions
For IOS, under the "ios" platform, set the "deployment-target" value to the currently released IOS version.

For Android, under the "android" platform, set the "android-minSdkVersion" value to the minimum supported Android API level. See Wikipedia page Android Version History for supported Android versions and the API level that should go in the config. Set the "android-targetSdkVersion" to the latest supported Android API level. You can find that in the previously mentioned Wikipedia page as well.

Important! Make sure you edit config_BoldNetMobile.xml and config_legacysecurity.xml.
Testing
I suggest testing on your local machine in Chrome because it's the easiest to debug with. Once you have it working in Chrome, check your changes into your branch. See Android Build and Apple Build for building.