Ancient Metallic Dragons (e.g. Ancient Brass Dragons) have the Change Shape ability:
Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon’s choice).
In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.
It is my understanding that the Spellcasting feature is a class feature and thus unavailable to an Ancient Metallic Dragon, but that the Innate Spellcasting trait is available to them.
Now, let’s take in example the Gloom Weaver humanoid from Mordenkainen’s Tome of Foes (p. 224), who has the following not-at-will Innate Spells:
1/day each: arcane gate, bane, compulsion, confusion, true seeing
If, say, an Ancient Brass Dragon decides to use Change Shape to turn into a Gloom Weaver, then decides to cast its 1/day true seeing, then uses Change Shape to revert to their dragon form, and uses it yet again to become a Gloom Weaver once more… does the dragon thus have a new use of true seeing?
In other words, does an ancient metallic dragon have essentially unlimited “X/day” innate spells by way of using Change Shape back and forth?