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No there is not. Once the app is updated by the developer, you then have to go to the required firmware to continue using it.

This is incorrect.

You can indeed download apps which require 4.2.1 even if you are on 4.1. Whether or not you can actually run the app is a different matter.

There is an iOS Version Faker out there, on some disreputable repo full of pirated software (which means I can't post it up).
 
is it possible to get past the app stores requirement on needing 4.2 on some apps?

Yes there are ways to trick the store to tell it that you are on a different version, however this is NOT recommended, those requirements are there not to "annoy" you, there is a reason, they use either new API (not present on your current iOS version), or they just don't work well under it, you can experienced memory leakage, slow down and crashes.
 
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