GETTING THE GILDED SWORD
There are 4 different swords in the game: Kokiri Sword (the one you start out with), Razor Sword (the one you can upgrade to, but it's not permanent), the Gilded Sword (the permanent sword), and the Big Fairy Sword (strongest sword in the game.) You start out the game equipped with the Kokiri Sword, and from there you can upgrade to the Razor sword, but when you go back in time, you lose the Razor Sword, therefore you must get the Gilded Sword. How do you get it, you ask? Once you defeat Goht (the Snowhead Temple boss) play the Song of Time Reversion, then go back to the main area of Goron Shrine (where the wooden cabin is.) Make sure you have the Adult Wallet and currently have 100 rupees in your inventory, then go into the cabin and talk to the blacksmith.
He will agree to upgrade your Kokiri Sword into the Razor Sword if you pay him 100 rupees. While he is upgrading, if you haven't yet gotten the Gold Dust and the empty bottle for placing first in the Goron Races, go and do that (see the proper section in the Walkthrough on how to access the Goron Races) then once you have the Gold Dust, warp to day 2 by playing the Song of Time Compression and go pick up your new Razor Sword. After you pick it up, give the Gold Dust to the blacksmith, and play the Song of Time Compression once again to warp to Day 3, then visit the Blacksmith one last time to get the Gilded Sword, and save your game right after you get it.