I installed E and now I can’t use Wifi. I want to revert back to my original ROM until this bug is fixed, so please tell me how to do that.
My device is Samsumg Galaxy note2 N7105.
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Did you make a backup of the original ROM before installing /e/? If so, you could install that ROM from backup.
Otherwise head over to XDA-developers. You can find an unofficial LineageOS-ROM there:
There might be other ROMs for your device there also.
I can not tell you, if the original ROM is available somewhere on the internet.
There are some suggestions on where to look for Samsung ROMs in this article What is a stock ROM and how do I get one?
how to do that is not part of the /e/ community. that’s part of the samsunf community. 
Mine is N7105. Is it possible to install it?
Do I use TWRP the same way as E to install the ROM?
If I find the ROM,how do I install it? Same as installimg E.
I used Odin. Thank you.
According to the /e/-device info page of the Galaxy Note 2, /e/ supports the Galaxy Note 2 with product id “n7100”. There is also a second /e/-device info page of the Galaxy Note 2 which supports the model “N7105T”.
Sorry, but I do not feel confident enough to answer this question.
Have you tried to use ADB (Android Debug Bridge), in order to get the exact product model ID of your device?
This question confuses me a little bit, because you would like to get a comparison between TWRP and /e/. I hope, the following statements help to clarify a few things:
In order to install an operating system, there are two necessary components:
/e/ is an operating system
TWRP is a recovery system
As far as I have seen, /e/ uses for some devices TWRP as recovery system (for example t0lte) and for other devices the LineageOS recovery system (for example xz2c).