What happens when a Shapechanged Dragon enters an Antimagic Field inside a narrow space? [duplicate]

A rather simple question: if an Ancient Dragon uses it’s Shapechange ability to transform into a medium-sized humanoid, and then has that Shapechange disabled/dispelled inside a narrow tunnel / small underground room, will they get crushed to death by their own size? I have plans on True Poly-ing my spellcaster PC into a Dragon, and i’m worried that a random dispel would instakill me when i go dungeon-delving in the Abyss or somewhere.

Can a shapechanged quasit use the blindsight of the bat form?

The stat block of the quasit gives under the shapechanger trait:

Its statistics are the same in each form, except for the speed changes noted.

So does a quasit will not have the traits of the "polymorphed" (earlier editions) form, like the Blindsight of a real bat (with a fly speed of 30 feet), because the quasit itself has no Blindsight in its stat block, but Darkvision 120 feet?

Can you benefit from Bladesong while Shapechanged into a Marilith?

Shapechange allows you retain your Intelligence & class features, while taking up your new forms’ physical stats. In theory, this means that a Bladesinger could change into a Marilith and get 7 attacks with crazy modifiers using Bladesong, while having really high AC and Concentration saves.

However, a few questions came up:

  1. Swords Not Included™: You would need to supply 6 melee weapons rapiers to benefit get the most out of Song of Victory. How could you effectively carry these before Shapechanging, and effectively wield them afterwards?
  2. Assuming this goes smoothly, would your weapon attacks be at +11 to hit (+5 Dex due to finesse + 6 proficiency), or the Marilith’s +9 (which appears to be +4 from Str, due to longswords not having finesse, and +5 prof)?
  3. Would the damage be 6d8 + 60 for the sword attacks (w/ Song of Victory), plus 2d4 + 9 for the tail?
  4. Would AC be 18 + 5 (Bladesong) = 23 (+5 optionally with Shield) ; and +15 Concentration Saves?

Granted, it’s no Wish, but vs a handful of powerful targets (especially with Spellcasting), I feel like it could really bring enemies down quickly and hold the line, ideally if Hasted by a party member.

Can imps talk while shape-changed to a form resembling a beast?

Can an imp speak while shape-changed? Another question on the same topic: is a shape-changed imp a beast?

The Imp has the following ability:

Shapechanger: The imp can use its action to polymorph into a beast form that resembles a rat (speed 20 ft.), a raven (20 ft., fly 60 ft.), or a spider (20 ft., climb 20 ft.), or back into its true form. Its statistics are the same in each form, except for the speed changes noted.

The spell Polymorph states:

The creature is limited in the actions it can perform by the nature of its new form, and it can’t speak, cast spells, or take any other action that requires hands or speech.

So the obvious answer is that it counts as a beast and can’t talk. However, it keeps all statistics (is languages and type included here?) and that it only polymorphs into a form resembling a beast, not that it polymorphs into a beast. Furthermore, is the shape-changing even using the same rules as the spell Polymorph?

Is there any consensus on what RAW should be? Any argument for what RAI is?

Does a creature Shapechanged into a Balor activate the Death Throes feature when reduced to 0 Hit Points?

Say a PC casts Shapechange on himself to turn into a Balor. This grants him some sweet abilities, such as:

Death Throes. When the balor dies, it explodes, and each creature within 30 feet of it must make a DC 20 Dexterity saving throw, taking 70 (20d6) fire damage on a failed save, or half as much damage on a successful one. […]

The player character drops to 0 Hit Points. Does this trigger this ability?

I’m guessing the answer is a no, unless the PC would actually die, since the character doesn’t die when dropping to 0—they simply change form—as per the spell:

If you revert as a result of dropping to 0 hit points, any excess damage carries over to your normal form.

Could anyone confirm or correct my guess?