Onilordasmodeus i have a question: in MK4, how could Shinnok be free, did Shinnok go to EarthRealm??? Cuz his amulet was fake in MK4.
When you ask "how could Shinnok be free", I'm guessing you mean why didn't the EGs know he was free.
Well, the short answer would be Quan Chi.
(skip to the TL;DR if you don't want to read everything)
Quan Chi, without the Amulet, has the power to open portals to "any" realm and go through them undetected by the appointed Gods of that realm, or even the EGs themselves. Also, the Netherrealm itself is a pretty inaccessible realm in its own right, as you can probably count on one hand the amount of characters, or times that a character, have actually physically gone there and gotten back out under their own power, without dieing and being resurrected, or without some ancient artifact to aid them. Not even Quan Chi can stay there for extended periods of time as he has to leave and comeback for fear of being trapped there himself.
It is worth noting that Quan has his own space in some unknown realm where he can astral project himself through dimensions as well, so sometimes he may opt to not go there at all.
Another point that has to do with Shinnok's banishing specifically, is that when he was banished to the NR in the first place, it wasn't the EGs who imprisoned him at all, it was Lucifer.
When Shinnok landed in the NR, Lucifer and his minions attacked him, imprisoned him, and tortured him for millennium; but when Quan set Shinnok free from the binds that Lucifer put on him, Shinnok took over everything in that realm. It is possible that the EGs weren't aware that Lucifer had been dethroned, nor that Shinnok had come to power, but most likely they just didn't really care what was going on, because the bottom line is that when Shinnok was sent to the NR, he was accepted by the realm (meaning his corruption tied him to the fabric of that realm), the Realm itself devours magic so Shinnok was presumably kept in a weakened state, and all of the magics that would have allowed Shinnok's return from that plane were hidden away and guarded, or lost.
Another thing to keep in mind too is that the EGs don't enter the realms AT ALL. Even at the end of MK9 they just sent there "power" into Raiden rather than go down and deal with Kahn themselves. The EGs actively try not to interfere with issues of the realms for "fear" of being corrupted by the One Being (like Shinnok was), so they instead let/instruct others do their bidding, and fight in their stead.
So, Quan Chi being a "mortal", and a free roaming sorcerer, and being Shinnok's right hand...coupling that and all the facts/info I put up top with the fact that the EGs don't really care what "mortals" do at all, and you can start to see how Shinnok and Quan Chi went under the radar to everybody.
TL;DR...
- Quan freed Shinnok without the EGs knowing since he is a free roaming sorcerer;
- Shinnok took over the NR during the time that Shao Kahn and Onaga were merging worlds and building their own empire (many disturbances in the "furies" and the EGs don't interfere with the realms directly unless there laws are explicity broken);
- Quan Chi had been studying the real Amulet for years before helping Shinnok escape in MK4, and he had many connections throughout the realms. He most likely had figured out/manipulated a way to free and mask Shinnok from even the EGs (like he does himself), and I think the big thing is that the portal that was opened for him was opened from the outside, from Edenia to the NR, not from Netherrealm to anywhere else.
P.S.
It is also worth noting that in the MK story, Quan Chi is a
very "special" character, with the ability to do things that no other character can do. In MKA we learned that all the corruption in the realms, even Shinnok's fall from grace,
may have been because of Quan Chi's influence (before he was actually Quan Chi).
At this point in the story, it is still unclear exactly
what Quan Chi is, but it is without question that he is more than just some simple, or even very powerful, sorcerer. Quan Chi just may be the One Being incarnate...that or just a very powerful emissary of the OB. Regardless, he apparently knows things that not even the EGs know, and they apparently cannot, or will not, kill/destroy him.
The "real" bad guy behind all the bad stuff that happens in the MKU is Quan Chi as he manipulates most everyone, and his influence corrupts everything.