I don't exactly know if this is possible, and if it is, I don't know how to do it, but I would really appreciate it if someone would tell me if it is possible to, through functions or datapacks or, if in 1.12.2, something to put in the "data" folder; To speed up the Brewing stand time and furnace time. Maybe its easier if you named it something and then the function sped up anything named that thing? I am just speculating. Thanks!
Last night as I was going to bed i was thinking to myself, "maybe its for 1.13" so that explains a lot. But thanks for the help! I will try it out in 1.13. Also, if you can speed up cooking, do you think its possible to speed up the chances for fishing, to make fishing super quick? maybe if you named the fishing rod a certain name and then used it like you used the scoreboards in the furnace?
So I tried it on 1.13 and it didn't work. So I don't know the exact command to give an armor stand tags, but I tried naming it "Furnace1" which was what I put in all of the commands. But it didn't work. and the last command that you give told me it couldn't find the entity. I don't know whats wrong...
For summon an armor stand tagged Furnace, use Tags:["Furnace"]. Make sure you put the armor stand on top of the furnace and replace all tag=Furnace to name=Furnace1. And your summon command is wrong, you don't need EntityData, just directly go to CustomName. And use Json format for CustomName, I don't know if it is required or not, but better use that.
Check the furnace, count the time when it is smelting. If it smelt an it in half of the time normally it does, then this works. The last command find an armor stand with score cookTime 100 and set it's cookTime score to 0, so it can find the armor stand in just 1 tick each 100 ticks.