I found this page the other day:
http://zeldaspeedruns.com/oot/ba/minigame-items-on-b and decided to research it further in OoT3D and see if there were any key differences and these are the result I've come up with so far:
I'll replace the Saving/Dying page with a temp B page eventually. Hopefully this will help people understand things better.
I still haven't looked into things like Lon Lon Stick (how things behave when you haven't equipped a sword yet)
Basically temp B is a temporary value stored in the memory so that the game knows which item to return to your B button after doing things which will replace the B button.
The same place in the memory is also used to decide whether or not your B button is grayed out, disabling it.
The game is set up so that it will return the value of temp B to your B button when specific events occur, if you have any item except for a sword on B. This leads to some interesting behavior which can be useful at times, but it can also be an obstacle.
There are also a bunch of things which will set the B button to 0 (Deku Stick), and others that will set it to FF/255 (Blank)
Storing B on temp B
a) Borrow Fishing Rod
b) Ride a Horse
c) Start Shooting Gallery
d) Start Bombchu Bowling
Setting temp B to Deku Stick (00h/0d)
a) Gray out the B button and highlight it again
b) Load a File
c) RBA
Setting temp B to Blank (FFh/255d)
a) Gray out the B button
b) Return Fishing Rod
c) Finish Shooting Gallery
d) Finish Bombchu Bowling
Retrieve temp B
a) Save with any item except a sword on B
b) Die with any item except a sword on B
This will also set Temp B to Deku Stick (00h/0d)
c) Enter Fishing Pond with Fishing Rod on B
d) Create a new File (NG+)
Can't retrieve Deku Stick (00h/0d)
Notes:
To escape the Shooting Gallery you have to use Restricted Items with Iron/Hover boots to get hit by a bomb during it. (Or have a timer expire warp during it)
To steal the fishing rod you have to use Restricted Items with Iron/Hover boots to get hit by a bomb while fishing, or warp out with Farore's Wind / timer expire warp.
The only way to escape the Shooting Gallery or steal the fishing rod as a child is by using Inventory Overstuffing to equip Iron/Hover boots.
Bombchu Bowling is only available after entering DC blue warp, making it impossible to store Temp B with it in an any% run.
Bombchu Bowling & Horse Riding are the only 2 methods which allows you to keep temp B that doesn't require iron/hover boots. This means that you can play through the game and save freely as long as you do not gray out the B button.
Fishing & Horse Riding are the only two methods where you can save during it. This means that you can use the Fishing method without Iron/Hover Boots, but you can't keep temp B when you leave the area.
Examples:
1. Start Bombchu Bowling with Kokiri Sword on B and exit building
2. Exit Game
3. Create new File
The new file will have Kokiri Sword on B
You can keep creating NG+ files as it doesn't clear temp B
1. Get Fishing Rod on B
2. Turn into child
3. Start Bombchu Bowling and exit building
4. Turn into adult
5. Save
You'll get Kokiri Sword on B as an adult
1. Get Bottle on B
2. Escape Archery
3. Save
You'll still have bottle on B
You can keep saving the game and keep the item until you gray out the B button
1. Get Bottle on B
2. Ride on Epona
3. Die
You'll still have bottle on B
However, temp B has been set to 00h/0d (Deku Stick), so you can't save/die without reverting the B item to a deku stick
1. Start Bombchu Bowling and exit building on a NewGame+ file
2. Save Game
You'll still have the NG+ item on B
You can keep saving the game and keep the item until you gray out the B button
