Also some other fixes were added up to 4.1 not sure how critical they are though. List here.
4.2 doesn't add any functionality, just mod blocking.
You should be on 3.2 or 4.1. Most people will find 4.1 to be just fine, there are some limitations that 3.2 can do that 4.1 can not. I don't know what they are, but it involves the fact the 3.2 has more vulnerabilities to exploit. But if you don't know I would recommend 4.1. Use the 3.1-4.1 guide below to upgrade to 4.1.
If you can not install bootmii as boot2 preloader or fork of is mandatory for a small amount of brick protection. Other than brick protection it also offers many useful hacks, like update blocks and autoload app or hbc.
Ipsa scientia potestas est.
Warning: Piracy is NOT supported. Word your questions carefully.