When you lock down a Lollipop device to disable Chrome's incognito mode, this creates an XML "restrictions file". What actual XML is inside the file?
The XML file alone will not help you. Chrome doesn't read the contents of that file directly. Instead, it accesses it via Android's UserManager.getApplicationRestrictions. In order for this to work, you actually need to set up a "work profile" on your device. In order to do that, you actually need to run the BasicManagedProfile app you have mentioned; this also requires encrypting the device.

Android 4.1.2 is kind of old. From searching at http://www.androidxref.com/, it looks like it lacks UserManager.getApplicationRestrictions. Luckily, there's another way to disable incognito browsing in Chrome. Try that way instead.