Magic Resistance. The genie has advantage on saving throws against spells and other magical effects.

 Gasious. Any physical action taken against the genie automatically fails, unless done with a magical item.

Shapechanger. The genie can use its action to polymorph into a humanoid or back into its true, gasious form. Its statistics are the same in each form except it strength which changes to the form form taken. When turning back to genie form any equipment it is wearing or carrying isn't transformed and drops to the ground. It reverts to its true form if it dies.

Innate Spellcasting. The genie’s innate spellcasting ability is wisdom (spell save DC 15). It can innately cast the following spells, requiring no material components:

At will:  minor illusion, wish, lighting bolt

IMPORTANT: when casting wish the genie does not replicate other spells, it uses it for creation (constructs, effects, illusions and other items of that sorts), magical/living items/creatures can not be created or destroyed.

Minor illusion

You create a sound or an image of an object within range that lasts for the duration. The illusion also ends if you dismiss it as an action or cast this spell again.

Lighning bolt: 

A stroke of lightning forming a line 100 feet long and 5 feet wide blasts out from you in a direction you choose. Each creature in the line must make a Dexterity saving throw. A creature takes 8d6 lightning damage on a failed save, or half as much damage on a successful one.
The lightning ignites flammable objects in the area that aren't being worn or carried.

Wish: 

• You create one object of up to 25,000 gp in value that isn't a magic item. The object can be no more than 300 feet in any dimension, and it appears in an unoccupied space you can see on the ground.
• You allow up to twenty creatures that you can see to regain all hit points, and you end all effects on them described in the greater restoration spell.
• You grant up to ten creatures that you can see resistance to a damage type you choose.
• You grant up to ten creatures you can see immunity to a single spell or other magical effect for 8 hours. For instance, you could make yourself and all your companions immune to a lich's life drain attack.
• You undo a single recent event by forcing a reroll of any roll made within the last round (including your last turn). Reality reshapes itself to accommodate the new result. For example, a wish spell could undo an opponent's successful save, a foe's critical hit, or a friend's failed save. You can force the reroll to be made with advantage or disadvantage, and you can choose whether to use the reroll or the original roll.

Multiattack. The genie can cast two spells in one action: wish and ligning bolt or minor illusion using one action