You cant, they never made it.
you cant fierce deity link is only in majoras mask
You can get the Fierce Deity Mask on the Moon.
Guess directions its random usually it goes right, left, right, right.
yes
complete all four dungeons on the moon giving up all 26 mask. do this befor you fight majora
You cant.
There is no Known cheat that allows you to get the Fierce Deity Mask with out collecting all the Masks.
Once you do get it from the majoras mask kid in the moon you must defeat the majoras mask and you MUST watch the credits all the way to the end once it says THE END and the sarias song stops playing reset or turn off your N64 then reopen your file you will notice the mask will say 24, now check your masks notice there right in the bottom right corner is the fierce deity's mask.
there is no adults mask but there is a fierce deity mask. You get it by playing all of the kids games on the moon. Also you need to have all the masks in the game to get it, thats very important.
beat the game 2 times and erase 1 file and use it and u will come out with the deity mask, or collect every single mask and give them to the children dancing around the tree on the moon, then speak to the kid with the majoras mask. once you've completed all four dungeons you will haave the fierce deity's mask, but no other happy masks. play the song of time to get them back ^NOTE TO ALL: The beginning of this answer cannot be done. If you beat the game two times and erase file 1, it won't do squat. But the rest is legit.
Obtain all normal masks. Then, have the giants stop the moon from falling. When on the moon, some...interesting people will take your masks when you play with them. When you don't have any more masks, talk with the guy wearing the majora's mask. No one wants to play with him. When you talk with him, he'll mention how you have no more masks to play with. Then, he gives you the infamous Fierce Deity Mask.
The Fierce Deity glitch allows you to turn to Fierce Deity Link outside of boss battles. There are a number of ways to do this; the most-well known involving a glitch in Sakon's hideout.