Accessing the main title screen file, also known as Back in Time (BiT) in other Zelda titles, lets you save the title screen file over the normal File 1 in the File Select screen.
This file has most items and equipment already given to it, but it is "untouched" in that world events haven't been triggered. For example, most cutscenes haven't been played before, so going into an area like Kokiri Forest will play the cutscene for when Link first steps out of his house. All chests are unopened, all upgrades are missing, etc.
When setting a Farore's warp point from boss rush, the game stores a base entrance index of -1. This index is special cased to send you back to the title screen if Link is spawned with it, essentially acting as if the game had been quit.
When you normally try to wrong warp with a blue warp, this reset doesn't trigger as it is overwritten by cutscene fadeout. If you return to a Farore's Wind point on the first frame possible, this reset does not get overwritten, and you acquire the next cutscene number value set by the blue warp.
The forest, water, shadow and spirit temple cutscenes set a value of 0000 when the fadeout occurs. From this value, the title screen cutscene is cleared and you appear in child Hyrule Field (a special cutscene map rather than the normal Hyrule Field) out of bounds.
Target the wall from the pillar that has the vines/ladder and position Link's left foot with the tile line:
Then sidehop left and do Restricted Items to open FW text box while touching the blue warp. On about the third frame where whiteness appears on screen, and based on the position of the blue prism, buffer "A" to get the warp successfully. (Watch video below to see what the frame looks like)
After successfully wrong warping, you need to void out a total of 14 times to die. After dying, hold L and roll forward a couple of times to land in the water. Save and Quit.
When performing this glitch, some data is transferred from the file you performed the trick on to the title screen file. The following is a partial list of data that is transferred over: