Far Realm was initially created by Bruce Cordell for the AD&D 2e module The Gates of Firestorm Peak. This module is dated 1996, so you cannot find any lore from, say, Planescape series of products. In the module, there is the namesake gate.
This gate is called the Vast Gate in Cordell's article "Enter the Far Realm" published in Dragon magazine #330 and ...
The Rrakkma adventure module includes a portal to the Far Realm
This adventure module for Adventurer's League includes a portal to the Far Realm, although it's up to you how "canon" you consider this.
In "Area 11. The Cathedral" of "Section 2. Temple of Madness", which is on the plane of Pandemonium:
Section 3 is then set in the Far Realm, although it's ...
Most elementals are native to the elemental planes
The Introduction to the Monster Manual (p. 6) and the corresponding portion of the basic rules mention in their description of the "elemental" creature type:
Elementals are creatures native to the elemental planes.
For these elementals, even when they are formed on the Material Plane, they are still ...
This is Homebrew, so it's up to the DM
This represents a change to the monster and determining how that change interacts with existing mechanics is up to the DM.
There is no right answer here from the community because we didn't create it and it really can interact in any way because of that. Whomever created it can decide how they want spells like ...
It was likely corrupted by a fiend
While I am unfamiliar with this AL module, the published adventure has a section very similar to what you describe:
This can be found in the "Path of Devils" chapter, page 107.
I will try to provide a somewhat subjective answer from 2e. The outsiders (as they got to be collectively called later in 3e) are beings that are the embodiments of their respective planes and everything in the Outer Planes is about belief. As such, the way we played 2e, we used to assume that the destruction of an outsider's material form should not be ...
The general rule is that creatures die when they reach 0hp; PCs being an exception.
The Monster Manual (p. 6) says:
Certain spells, magic items, class features, and other
effects in the game interact in special ways with
creatures of a particular type. ...
The game includes the following monster types, which
have no rules of their own.
There are no rules for this, but you can take guidance from AD&D 2e and/or D&D 3e.
There is an interesting section on The Inner Planes in the Dungeon Master Guide revised edition of AD&D 2e:
The Inner Planes
Using the sphere analogy, outside of the Primes and the Ethereal
planes are the inner planes, the primary building forces of the
I think that if, for example, the plane of air and the material plane collided, portals would open, gravity would become more of a guideline than a law, and winds would become stronger. Towards the planes of ice and ash, the air might become hotter and dryer, and ash might rain from the sky, or glaciers would pop into existence, the air becoming freezing and ...
It will work fine on the outer planes
The limitation on the Etherealness spell is just that; a limitation on the Etherealness spell. Blink has no such limitation.
However, your DM has to decide if you can see the outer plane you left.
While on the Ethereal Plane, you can see and hear the plane you originated from ...
From the DMG (p.48):
Great Wheel—1e kinda, 2e, 3e, 5e
You are correct that the Great Wheel cosmology was used in at least 2e, 3e, and 5e. It was codified, and most thoroughly detailed, in 2e’s Planescape setting.
Prior to Planescape, the cosmology wasn’t named, but nonetheless something sort of like the Great Wheel had been gradually developing and emerging from the various ...
I would say that if interpreting the banishing arrow as a means of movement between the planes (in this case both forward and back), the Dimensional Shackles would prevent the secondary trip back to the plane of origin.
In addition to serving as mundane manacles, the shackles prevent a creature bound by them from using any method of extradimensional ...
The creature remains in the Feywild
According to Dimensional Shackles:
the shackles prevent a creature bound by them from using any method of extradimensional Movement
The only "return clause" in Banishing Arrow says
At the end of its next turn, the target reappears in the space it vacated
If its turn passes and its unable to fulfill Banishing ...
You enter the new plane whole
From the spell description:
Your astral form can freely travel through the Astral Plane and can
pass through portals there leading to any other plane. If you enter a
new plane or return to the plane you were on when casting this spell,
your body and possessions are transported along the silver cord,
allowing you to ...