I have created a trigger zone to make sure that only only gameobject passes through it at a time. The moment the gameobject1 entered the trigger zone, it is given a particular tag but I am not how to stop other gameobjects from entering the zone. Is it possible to have two trigger colliders attached to a same object like an outer and inner trigger such that only one gameobject is allowed to pass through the inner one while all other gameobjects wait at the outer one.
If you need to have multiple trigger zones around your GameObject, you can add empty GameObjects as children of that GameObject and add the colliders to those children. You can then assign different tags to those child objects to be able to differentiate between outer and inner trigger zones in your code.
I would have made this trigger a solid collider and edit the Layer Collision Matrix (found in Edit>Project Settings>Physics) to make it not interact with gameObject1, given a special layer.
More info on Layer Collision Matrix: https://docs.unity3d.com/Manual/LayerBasedCollision.html