Since there are a lot of questions regarding the upcoming TN-V4 release, I decided to write this FAQ about the TN-V4 update and the future kernel mode exploit. Let’s get started!
At first, let’s clarify what TN-V4 actually is.
TN-V4 stands for Total_Noob V4. It is an eCFW (emulator Custom Firmware) for the PS Vita devices. It will be the 4th revision of said eCFW, and adds some new features, fixes bugs of TN-V3 and TN-V4 will be shipped for every firmware (At the time of the release) of the PS Vita. This would, at the moment, cover firmwares 1.00 up to 3.00. This will get rid of the above/below firmware 2.02 gap, that we at the moment have.

What can we do with TN-V4?
TN-V4 is the most popular PS Vita eCFW. It does not only support the playback of game backups (ISO, CSO), but also supports the usage of Plugins (VSH, GAME, POPS), PSN titles (PS1, PSP), Homebrews, 1.5 kernel Homebrews and even custom PS1 backup.
The best and unique feature, which just TN-V offers, is the complete PSP XMB. You get the operating UI of the PSP, including the VSH and Recovery Menu. Using VSH plugins like Dayviewer or CXMB? No problem with TN-V.
TN-V can also access the PSP PSN Store, so you can download all your PSP related PSN titles, even if your PS Vita firmware is not the most recent. Those downloaded titles will just appear inside of TN-V, not at your Vitas LiveArea. Downloading of PS3 or PS Vita content won’t be possible.
And who knows, Total_Noob might have some more surprises for us.

Can I use TN-V4 at my PS Vita? I have ‘insert exploit game’ and I am running the firmware ‘insert firmware version’?
This depends on your PS Vita firmware and the games you own. Just look at the following list, and you will know if your game/firmware will support TN-V4.
The ‘YES’ just applies, if your firmware is low enough.
For example: Running TN-V4 with Apache Overkill is possible at firmware 1.80, at 2.02 and also on 2.06.
But if your firmware is 2.12, then you won’t be able to use it with Apache Overkill.

I am using a Vita Half Byte Loader (VHBL), can I upgrade to TN-V?
If you are using a VHBL at the moment, then you will be able to upgrade to TN-V4. The day the files get released, you will be able to upgrade from VHBL to TN-V4.
When can we download TN-V4? Can I be a beta tester?
Total_Noob himself said, that he wants to release TN-V4 for every known PS Vita exploit somewhere between November 2013 and January 2014.
TN said that TN-V4 is pretty much finished, so I would guess that he does not need any new beta testers.

Firmware 3.00 (and newer) are missing in your above answer. Does TN-V4 not support firmware 3.00?
Total_Noobs 4th revision of his TN eCFW will of course supports the firmware 3.00, but for that we need a new exploit game, which isn’t publicly known yet.
There will be a new exploit game for the 3.00 TN-V4 release, but until then be sure to have a account, which is in a good stand. Registered users will see a ninja release, at least, 1 day before we publicly announce the new exploit game.

Does TN-V support my PS Vita Slim (PSV 2000) or PS Vita TV (PSV TV) device?
To be honest, we don’t know it YET, but we expect that TN-V will just run fine at both of these new hardware models. If you own one of these devices, feel free to try to get the TN-V exploit, because there is a high chance that it will work.
Should I update to firmware ‘insert firmware’ and use ‘insert exploit game’ instead of my current exploit game?
This is entirely your choice.
Updating the firmware will offer you every new feature of the new firmware, including the ability to play Vita games that require a new firmware.
The only difference between the firmwares is, that you have to know which exploit game is for which firmware. The second interesting difference will be explained in the last part.
Is there a major difference between running TN-V4 at a lower or higher firmware?
There is one major difference in using TN-V4 at a lower or higher firmware, and that gap is at firmware 2.12.
If you are running TN-V4 at firmware 2.12 or below, you will be able to get nearly the full 64MB of RAM, which enables you to use plugins and homebrews that were made for the PSP 2000 series and later PSP models. Your TN-V4 eCFW is basically a PSP 2000.
If you are running TN-V4 at firmware 2.50 or above, you will be able to just get the normal 32MB of RAM, which will let your TN-V4 eCFW act like a PSP 1000. This prevents the usage of PSP 2000 (or later models) plugins and homebrews.

Do you have any Firmware/Exploit game recommendations, The Z?
It is recommended to use firmware 2.12 and Fieldrunners for getting the best experience of the TN-V4 eCFW, because that way you are able to get the 64MB of RAM, the fastest launching exploit game (ever), and TN-V4 itself.
If you want to use the 32MB variant of TN-V4, then it might be recommended to use firmware 3.00 and the new exploit game, that we still have to announce. That way you’ll get TN-V4 and PS4 compatibility.
In the end it is your choice which exploit and firmware you want to use, but keep in mind, that the first firmware AFTER the TN-V4 release WILL fix TN-V4 and that the next public release of yet another eCFW might take again 6-12 months, maybe forever.