[Galaxy Note II Q&A, Help & Troubleshooting] aukhan:
EFS file is where your Imei , Mac address and few more important files are stored as you phone doesnt have an IMIE it shows as unknown so that is the reason your unable to make calls or the Sim is not getting registered, What you could try is to Flash a Stock Firmware and check if the IMIE shows up or else will have to take it to Samsung Service Center and will have to Pay for the Service.

The Guide which you've Followed dont say that you will have to backup the EFS Folder i've informed to update it on OP any ways not your mistake .

Always remember 1step after Root is to backup EFS File

Getting to know your EFS folder on Samsung Devices

Common Files We Back up

I am sure you have heard of critical things you need to do when you mess with an Android device right? One of the things that always come up is to back up your devices.

Backing up data usually involves making sure those contacts, calendar entries, memos, messages and special media that you may have kept within the internal memory are kept safe. The general rule when flashing and rooting is that often times, you may have to end up wiping all your internal memory data.

Some people tend to take this further and back up the internal data of apps, which is only possible if you have root access on your device. This is especially useful for those who like to play games as well as flash custom ROMs.

There are those who would also recommend that you back up the entire image of your current ROM state by making a Nandroid backup so that you can get back that exact state of your ROM if you mess up with flashing a whole new one or if you didn’t like the new ROM you tried and wanted to get back.

For Samsung devices, there is one other thing you may want to secure in a back-up chest – your device’s EFS data.

What is an “EFS”?

EFS refer to a folder location called /EFS in Samsung’s Android devices. It is a very sensitive folder hidden within the deepest core of your smartphone’s internal file system and is very essential to the functions of our smartphones.

One of the very sensitive information you can find in this folder is the information regarding your phone’s unique IMEI number. As you may have guessed by now, it also contains other unique identifying numbers for your smartphone including the MAC address for your smartphone’s radios, as well as the MEID, ESN, as wells as the registered phone number for locked smartphones.

The Danger to EFS

Normally, the EFS folder is highly protected. Rooting and flashing ROMs normally do not touch this part of the device. Unfortunately, there is no such thing as a controlled environment where everything goes according to plan in the real world. Sometimes, a process hits the EFS folder, or ends up corrupting the data within.

The EFS is also likely to be corrupted by users who like to unlock smartphones since it usually involves editing the data within the EFS folder. Once the data is corrupted, the only way to get it back to working order is to restore the data as is.

The loss of the EFS folder may cause your phone to no longer be recognized by your carrier or some of your radios may no longer work. This breaks the device as a whole no matter how many times you reinstall a ROM.

Even if you are not planning to modify the EFS folder itself, you can still accidentally corrupt that data. That is why even if the process of rooting and flashing ROMs does not require you to do so, it would be prudent to back up the folder. This would be a classic case of being “better safe than sorry”.

Why Modify the EFS

Messing with the EFS is what you would call some “high level stuff”. People normally don’t mess with this folder due to the high risk of making the smartphone unusable. The most common use of editing the EFS folder is to unlock the smartphone so it can be used on other carriers.

Most users usually steer clear of this folder. If you really want to mess with it, look for us tomorrow as we show you how to back-up your EFS folder.