You can breathe both air and water.

You are Proficient with intelligence (Arcana) and Dexterity (Stealth) checks, and you have expertise with wisdom (Perception) checks

You can use an Action to make an exhalation of magical energy in a 90ft Cone. Each creature in that area must make a Dexterity saving throw (DC 8 plus your Constitution modifier and Proficiency Bonus). On a failed save, a creature takes 14d8 Force damage and having their movement speed reduced to 0 until the end of their next turn or taking half damage only on a success.

You can use this Breath Weapon a number of times equal to your Proficiency Bonus, and you regain all expended uses when you finish a Long Rest.

You have Resistance to Force and Psychic damage, you also gain immunity to the Frightened and Prone Conditions

You have Darkvision with a range of 120 ft and Blindsight out to 60 ft

As a Gem Dragon, you have the innate ability to cast some spells. you know the following spells,  requiring no spell components and using Charisma as the spellcasting ability:

blink, control water, dispel magic, freedom of movement, globe of invulnerability, plane shift, protection from evil and good, sending

You magically transform into any creature that is Medium or Small, while retaining your game statistics (other than its size). This transformation ends if you are reduced to 0 hit points or use a bonus action to end it.

As a bonus action, you magically teleport to an unoccupied space you can see within 60 feet of you.

You can speak telepathically to any creature you can see within 120 feet of you. Your telepathic utterances are in a language you know, and the creature understands you only if it knows that language. Your communication doesn't give the creature the ability to respond to you telepathically.