Lets see this
1: What if Darunia was successful in defeating Volvagia?
Answer: you guys already did answer it but I have to give my piece of information as well, It is true, One cannot be named sage until upon death, an example is Nabooru, Ganondorf's wife, who is murdered by Twinrova infront of player's eyes, and later ascending as a sage, so the scenario is: Darunia wouldn't be a sage and would still be alive, Link will be given the fire medallion by the ancient sage of fire, and his quest will be continued.
2: What if Vaati Killed Ezlo instead of turning him into a hat?
Answer: tough!! Link is able to turn into Minish size because of Ezlo! entire dungeons for goddesses' sake is in the tiny size of minish, Link would NEVER complete his quest in fixing the sword, Vaati will suck the light force out of Princess Zelda and rule Hyrule as a dark god.
3: What if Link was too late and arrived after Great Deku Tree's death?
Answer: Link and Navi will be at loss, as Navi never got the instructions herself, "go get me the boy without a fairy" was the only thing she was told, and with the abstinence of Link who will probably never even leave the forest, Ganondorf will collect the stones from the dead old tree, the rock men who are starving, Darunia will probably give the stone to Ganondorf just to free the caves from dodongos so his people don't die off starvation, Ganondorf will forcefully take it from Princess Ruto as well, but Zelda will escape with Impa, holding the Ocarina of Time, putting Hyrule into a weird state, Ganondorf ruling the land but without true power as he is unable to access the Sacred Realm and the Triforce, and Zelda with Impa hiding in the shadows probably raising an army to strike back at the gerudo. (Whoah this turned into a new game)
Now let me If.
What If Tetra and her crew of pirates never went to Outset Island?