As I've already pointed out in my comments on the question, modifying your device's build.prop to appear as a different architecture is a very bad idea. It won't "hard-brick" your device, but certainly will have side-effects you won't like (e.g. the device might refuse to boot up at all – not sure what exactly will happen, as I was not yet bold enough to try; if you really want to know that, either try (not recommended if you don't know a way out then) or ask that as a separate question).
Concerning your real goal: As pointed out in my answer here, you can use Raccoon on your computer for that.
While the other question focuses on apps you've bought, Raccoon of course also works for free apps. For different device architectures, you will need to create different profiles: DummyDroid can create the required "GSF IDs for mock up devices" if you don't know the one of yours, based on the given device's build.prop. If that doesn't work out, or you want to use the "real ID", please see my answer here on how to obtain it from your device (or from that of your cousin).