I'm just answering off the cuff
Who created hell and when was it created?
hell, 'gehenna' or the 'lake of fire' I think is only referred to in the NT. I think it is a residence after the final judgement. Does it exist now? Hard to say because heaven time is not necessarily the same as earth time. It does not necessarily work by the same rules as our spacetime. Might be a different timeline. For our time, I think many would say sheol (a temporary residence for the dead) always existed, but hell (gehenna) is the final place where even death will die.
why does Genesis not say that in the beginning God created the heavens, a fiery hell and the earth? why was it not made known from the outset that if humans disobey God's commands they would be escorted to this place upon death of their flesh and bone?
I believe Genesis only tells us a little bit based on what we need to know. It's not exhaustive or analytically detailed. In fact I believe it might be talking about a recreation after the fallout of satan's rebellion, not the original creation of the earth. BUT I could be wrong, god is free to correct me.
what about the first created human couple (adam and eve) after their death were they sent to this fiery hell? and who escorted them to this place?
Did adam and eve go to sheol? Maybe, but I doubt they went to hell, because before Christ how could there be a final judgement.
where is this fiery hell? is it in another dimension? how can the flame burn outside of planet earth it would need the right conditions to burn which has to have the same chemical elements and natural conditions that planet earth has? how can a spirit person feel pain if there is no flesh or any nerve endings?
I think you pose some good answers to your own questions. Heaven and God's realm I think are a 'dimension' which contains our dimension. Our physical phenomenon like physical fire and physical pain function by the rules of our lower dimension, but they are parallels of greater realities which are not limited by the same rules -- although they still function by certain principles... what you might call God's truths.
is hell really a flaming chamber of horrors and torment everlasting where bad spirit creatures reside and where sinful or wicked and unrepentant human beings go after their death on earth? or is hell symbolic of something else by association? is hell just the abode of the dead where life just ends and nothing else can ever happen except that the very fibers of your being returns to the chemical elements that flesh and bone was created from in the very first place?
Some people hold that the meaning of 'unquenchable flames' is that the flames are unstoppable until they have completely consumed. Meaning that they completely destroy the souls ... not that they go on burning forever.
As for the nature of the punishment, it is also said that it is the result of people being allowed to be their own gods or have their own gods, while being completely aware of the truth of the real God... that it is a sort of 'be careful what you wish for' because they get what they wanted but it was a foolish thing to want, and that is where the torture comes from. Ultimately self-induced by the revealing of their nature.
I can't say if it's everlasting or simply unstoppable annihilation. But I do believe the suffering is a result of people realizing the truth of what their lives revealed about their eternal nature. God have mercy on us all.
I wonder what the real truth is about hell? can there be many truths or just the one truth? if there is only one truth then why is there a difference of interpretation and opinion of the Holy Scriptures?
There is One Truth but it is so vast and onwards-expanding that it will take all of our perspectives unified in Christ to see it fully. There is difference in interpretation because the enemy labors to keep us divided, because there is a spiritual war in this time. The key to seeing the whole truth is seeing God... focusing on the father, son, holy spirit, as people, relating to them as people. We can't handle the truth without them, so when we try to do it our own way outside of relationship with them, we inhibit the process of growing up in that truth.
God bless you brother. We don't know it all and that's ok because we know who does.