Sorry, but iOS 4.2.1 is the last version an iPhone 3G can run. It was, unfortunately, the choice of the developers to only support iOS 5 or higher, so there will be no way you can run those apps on your iPhone. Your iPhone will of course continue to work just fine doing what it's always done.
iPhone 3G is Old technology. When it was launched it had iOS 2.0. Currently, the highest it can go is iOS 4.2.1 and therefore can not handle many newer applications. As you have recorded, it is giving good service for which it has been designed.
Needless to say, if you want to use applications as stated, you must have at least 3GS, whose current is iOS 6.1.2. On the lighter side; Rather than updating iOS they are asking you to update iPhone (Technology). Cheers