I bought this KIT about 7 years ago.
I didn’t know a Arduino at the time, so I gave up halfway through. I’ve studied it since then and want to get it up and running.
Are there any information, document and code?
What do you want to do with it?
There’s still a lot in ‘Learn’ that’s specifically for the emonTx V2, and in ‘Resources’ there are links to V2 and GLCD data (these take you to Github and the sketches, and if you go far enough down the list, you’ll come to the NanodeRF).
We still use the same processor, so all the modern sketches will work, but some, particularly the latest CM (Continuous Monitoring) ones, would need the RFM69CW radio, so unless you can change the RFM12B which you have (very difficult without the proper tools), you won’t be able to use those and the radio (but you will be able to use the emonTx with a wired serial connection to (say) a Pi Zero W and do continuous monitoring). The real difference will be the I/O - what the inputs are used for has changed over time, but I have a table listing all, so that’s not a real problem.
And I have a “debugging” sketch for my emonGLCD that I use to see exactly what the Tx is transmitting - and I use it regularly. 
But I don’t use the Nanode RF.
I want to know how do I operate them. And I want to re-write the code.
You use the emonTx V2 in exactly the same way as you use the latest version, the V3.4. It broadcasts the data (at 433 MHz, from the length of the antennas you have) to both the emonGLCD and to the NanodeRF. The GLCD displays the present readings, the Nanode sends the data via Ethernet to a database - usually emonCMS, that can be either emoncms.org, or emoncms running on your own server, which might be a Raspberry Pi. emonCMS produces web pages to display the data.
You will want to study the sketches for all of these - they are on Github. Links for the modern sketches, the GLCD and the emonTx V2 are in Resources, you’ll need to to go to the top of our Github to find the NanodeRF sketches etc.