Tomato and Router Talks

Having never used Tomato myself, I'm hoping you experts can help me understand the lingo.

I was going for this one:

tomato-K26USB-1.28.7476MIPSR2-Toastman-RT-Ext.trx.zip

because it's on your forum and most used, and I don't know any better.

My friend recommened this:

tomato-K26USB-1.28.7486.2MIPSR2-Toastman-RT-VPN+NOCAT.trx

because it's a newer build.

Now I agree that newer build is better, cause it should have less bugs, more features, more security and greater stability. But since I don't know much about router lingo, what it means to me is confusing.

To me:

VPN means: the ability to set up a private network

NOCAT means I cannot use my gigabit LAN ports... which would suck, since that's partially why I bought this router.

So can you guys help me understand the lingo:

What do these terms mean:

MIPSR1

MIPSR2

VPN

NOCAT

RT

VLAN-RT (Virtual LAN-RT?)

RT-MINI

RT-Lite

RT-Ext (Extended? The Ext file is much larger than the Std, which is larger than the Lite)

RT-Std (Standard? what exactly is standard?)

RT-VPN

NoUSB (I'm guessing can't use the usb port on router)

NVRAM (Non Volatile RAM? What does this have to do with the firmware?)

VLAN-RT-N

IPv6

why are some (tomato) files .trx and some .bin?

Also I was told that my WNR3500L router is a MIPSR2 router, is this so?

and  here:

http://www.myopenrouter.com/article/13860/WNR3500L-Open-Source-Guide-Res...

a post where the author is written as NETGEAR, says the chipset has a "Dual band radio transceiver". I know for a fact that the WNR3500L can have dual WANs. A main WAN and a Guest WAN (not sure if it supports more, only now learning about it). But on the box and site where I bought it says "IEEE 802.11 b/g/n 2.4 GHz", which means it's single band. Can anyone give some insite on this? Is the dual band radio transceiver simply referring to the dual WAN or can I install firmware in it to make it a true dual band?