should have made a nandroid backup before flashing the superman rom. do you still have custom recovery? if so just flash another custom rom.

 

and just to be sure, you are flashing roms specifically made for your model, correct? roms are very device specific.

 

Maybe tell us what problems you have flashing the stock firmware, so someone can help with that?
(Won't be me, as I've never flashed a Samsung, but there are plenty here who have).

If you can get that done then take a nandroid before trying to flash any ROM, so that if there's a problem in future you can just revert (my standard advice is to take a nandroid before flashing anything at all, including the patches to root the phone).

Meanwhile, since all of the ROMs have this problem there are two possibilities: the first ROM flash you did did something that the others aren't undoing (i.e. contained more than just the ROM), or that all of them have some common feature that makes them all incompatible. That last might be possible if e.g. they are all based on a version of Android that requires your system firmware to be newer than it is: there's a lot more to the system firmware than just the ROM, and a ROM flash won't update things like the baseband firmware, so if it's something like that you might need to update to the latest stock firmware via Odin before flashing these ROMs. Maybe find a ROM based on the Samsung ROM close to what you last had working (same Android version at least) and see whether that works?

 

The first thing I do immediately after flashing custom recovery (TWRP) and before rooting is make a Nandrpid backup with all partitions checked and save it to external sd, OTG flash drive and/or pc. Even if you have a backup of previous working rom. You may be able todirty flash one or several partitions. Its my opinion the imei number is the cause of your sim card not being read. The official factory firmware does not include the imei and therefore , I'm sorry to saywithout a nandroid backup you may be SOL .

 

just an fyi there's a lot of models for thge s7 edge:
https://www.techwalls.com/samsung-galaxy-s7-edge-model-numbers-differences/comment-page-1/#:~:text=The model number of your,are for Galaxy S7 Edge.

and like i said roms are very device specific. make sure the roms are for your specific model.