A glitch returning from OoT3D, the Restricted Items glitch (or RI for short) allows you to use items that you normally would not be allowed to use. Allowing for the use of items in other forms such as Deku Link and giving you the ability to use Fierce Deity Link anywhere.
Unlike OoT3D, you can't just pause and unpause to do RI. You need either a Deku Flower, perform Down A or the Pictobox to do RI.
To use Pictobox RI you must:
1. Switch to the Pictobox
2. Open your items and swap two items around, one being an item you CAN use, and one you CAN'T use.
3. Back out of the menu
4. Back out of the Pictobox and press the button for the item you can't use.
By performing Down A either being Swordless as Human Link or having your B Button dimmed (be inside a house or use the blast mask), your X,Y,1,2 buttons will not be updated from their current state meaning that switching from a mask to bombs while in Down A, will let you use the bombs.
This method only works on 0th day in South Clock Town. To get to this glitched day, do Gibdo Mask BA between minutes 1:24-1:40 after starting the game. The time will enter in seizure mode, so play Inverted Song of Time to stop it. And then warp out to clock town.
Get the carpenter close to the mailbox and talk to him to activate text storage (it will display ERROR*** for a brief moment). Check the mailbox then walk away from it, close out of the menu and if there was an item/mask you couldn't use before, now you can use it. Note: L Targeting and changing an dimmed item with an usable item in the Items Screen, will cancel RI.
Similar to the Down A method you can use restricted items by grabbing a ledge on one frame. You must enter the items menu as you grab the ledge, then swap the restricted item with with one that you can use and as you exit the item select screen, press the button with the item on it. This only works with ledges that force Link to pop up (For example every ledge as Deku or the ledge in the milkbar)
When it comes to swapping items, before opening the Pictobox one item must be an item you can use in your current form. For example, having the hookshot on X and Fierce Deity Mask on Y then follow the steps above. An empty item slot can also be used to Pictobox RI, allowing you to swap spots with an item that isn't there.