Amulet of changing forms

This amulet is constructed from a circular piece of jade surrounded by gold connected to chains of silver. there are silvery runes etched on the gold and on the jade. 

while wearing this amulet you gain the following benefits all of whom manifest by changing your physical and visible form:

• You can cast Polymorph, on your self, twice, after you cast it twice you must finish a long rest before you can do so again. You gain a +3 to constitution saving throws made to maintain concentration on polymorph. when you cast Polymorph with this feature of the amulet, you can choose to transform into a creature from the list below (but still abiding the other restrictions of the spell including the challenge rating restriction):  

    Wyvern, Hippogriff, Griffon, Owlbear, Winter Wolf, Bulette, Behir, Chimera, Hydra.

Additionally you can choose to transform to humanoid form from the following list (but still abiding the other restrictions of the spell, and you maintain your proficiency with skills and tools, you don't gain proficiency with the skills and tools and weapons of the new form, and you maintain the ability to understand and write languages you know, and you can use your hands but you still cant cast spells, your gear doesn't meld into your new form and you can use it):

   Commoner, Dwarf, Commoner, Elf, Drow, Orc, Halfling Commoner, Duergar, Commoner, Commoner, Gnome. 

• you can cast each of the following spells, on your self, once a day: Jump, Longstrider, Alter Self