Write in the seed you want then back out to where you choose between your three save games. Then go back in and start your game normally. It will sill remember the last seed used, and you'll be able to unlock stuff.
OH. Dang it, for some reason I'd only tried backing out to the first select screen, this didn't cross my mind.
WORKS --
Ok --
PS4 and Vita users who plan on platinuming the game, bookmark this post. This works on the current patch (1.03, I believe).
To get early 'infinite D6', Meat Boy/Girl, Etc.
Use seed SCHS XTT4
Enter it, then back out twice to load screen, then start new Isaac (D6) game on normal.
First Floor Notes
-There will be no keys on the first floor.
- The treasure room is fairly worthless. Unicorn horn or Ankh if you d6. You don't need to pick up either.
- Don't bother going right from start. It's a time consuming Envy that only drops a coin.
- In the spider room, if you can get a spider to blow up near the X tinted rock, you get 2 souls hearts. You probably don't need them, but better safe...
-In spider room, top right pot has a swallowed penny. You'll make tons of cash next floor, but just in case get this. Use your 1 bomb or kill a spider near it.
-secret room - skip it
-super secret room - skip it
-you'll be fighting The Haunt, so those extra soul hearts might come in handy since you don't want any red heart damage on floor two. EDIT - -nm, you'll be getting the goat head soon, so damage doesn't matter since once you reenter boss room on lvl2 the door will open if you have the GH.
Floor 2 Notes
-Go left one room. This will give you a key.
-Go back right, then up twice
-Use key to get in shop
-Buy Sharp Plug (!!!!!!!!!!) on sale for 7
-bomb up to secret room, bomb right to Treasure Room and you have Scapular! (you spent one bomb on floor 1 to get swallowed penny, got one on way to shop, and will get two in secret room to get you to treasure room)
-One D6 on the boomerang in the store will get you Stopwatch! (Note- you could also cycle through to Habit, though it works either way)
-super secret room is just hearts -- skip it
Here is where it gets interesting:
1) Kill Boss. If you need angel items, go into Devil room but DO NOT take anything.
2) Use infinite D6 on boss room item till it becomes an activatible item -- it takes awhile, but iirc the first will be Book Of Invincibility. Leave it there, it's a 'storage' locker now (more on this later).
3) Go to Arcade
4) Play shell game. After 5-10 rounds, he'll drop a troll bomb on himself - be ready for this and shoot it off the shell guy so he doesn't explode. a few rounds later you get the Skatole! Leave it there as a pedestal item to reroll. (if you need gold, remember you can use blood donation, and that damage gives you gold with your swallowed coin)
5) Use Blood Donation machine. At half health, your Scapular triggers, and you get 1 soul heart. Leave room, do again, leave room, do again, etc. You'll do this for awhile until it breaks and leaves a Blood Bag.
6) IMPORTANT - do not pick that up, or ANY coins (picking up a few by accident is fine, just try to avoid it).
7) Use slot machine till it blows up and leaves a dollar bill. Do NOT pick this up either. You will be rich without it.
You now have three pedestals to infinite reroll, and you should have a ton of coins / hearts/ etc everywhere.
8) You're going to be rerolling these three for ages. You should be watching for Monster Manual, D20, Pyromaniac, Tarot Card Generator (don't know name) and Epic Fetus
Depending on how many pedestals you got, order changes slightly but it doesn't matter.
A) When you see the Monster Manual -- take this, go over to boss room, and switch it with the Book of Invincibility. Now you have the MM for later.
B) Even though you need a bomb making passive for this, skip over Ipecac. First, it's faster to keep rerolling an extra pedestal, but more importantly you'll be burning through pretty much every pickup during this so it's best to get Epic Fetus which maxes your damage w/o any other pickups. (the fetus with a black lid).
C) Take Pyromaniac when you see it.
D) When you see the tarot card generator, leave the room and go to an empty room. Use infinite trick about 10 or so times until you get the judgement card. I keep this card out of the room in a safe place and grab it before I leave the floor. You can use this to get an extra item in a devil/angel room or a secret room. (note - be careful and don't pick up Missing No. in a secret room, you'll reset your build to crap. I did this by accident and had to start over). Go back to your D6 now and keep going.
E) When D20 drops, grab it.
As soon as you get the D20,----------
Keep doing the infinite trick, but now with D20. It will not reroll your D6, just coins/hearts/wealth from chaos etc. You should have dozens upon dozens scattered around from rerolling while having the swallowed coin, a new coin every time. Leave room and recharge your D20. Now open chests (do this with a full charge, because empty chests will get rerolled, but if you leave room to charge D20 they disappear).
Keep rolling D20 until you
a) get the Goat Head (ensures devil / angel rooms for rest of run)
b) get a couple more pedestal items (don't pick them up), this speeds up the process later.
Once a/b are complete, go back to your D6.
Start rerolling all the pedestal items (I had like 5 on the screen) until you get Epic Fetus.
You now have two ways to do infinite rerolls... you can trigger Sharp Plug to wound yourself, and then bomb yourself to heal. Going forward, remember Sharp Plug only works with NO charge. Next store I'd reroll till habit, just in case so you don't accidentally have a angel/devil room you can't reroll.
At this point, thanks to RNG you're pretty much OUT of all pickups and you should be just getting lunchboxes (add heart). But it doesn't really matter, you have epic fetus and infinite health, you don't need anything else for this.
F) Now, go back to boss room. Flip out your D6 for the MM. Go to empty room, and sharp plug / bomb heal till you unlock Meat Boy /Girl.
G) You're done with the MM, so grab your D6, any money/items lying around, and move on to next floor.
H) You can now infinite reroll Angel Rooms on future levels -- I"m in the midst of doing this, so I don't know how many item ones you'll see, but it is what it is. I'll also be looking for a secret room with an item since I need Undefined, and I'll report back if i find one.
WARNINGS / how to's
-You now have infinite D6. Be careful, improper use of the combo is an easy, stupid death.
-If you avoid red heart damage on floor 2, after fighting Monstro you will get a devil deal.
-If you don't take the deal, and don't take red heart damage on floor 3, you will get an angel room. (note -- 1 time i didn't, but i got it on the next floor
-be careful clearing rooms once you start rolling D6... sharp plug only works with NO charge, so if you clear a room you'll get 1 charge and be locked out -- you can fix this once by buying the battery in the story, but after that you'd be screwed.
How to use the combo:
-The goal is to get down to exactly one half a heart. This will trigger scapular, giving you 1 soul heart ONCE PER ROOM -- exit and come back every single time. Room does not need enemies.
-With half a heart and NO charges, using your collectible will trigger sharp plug. You'll take damage and fully charge your d6. However, your single soul heart will be taken, you'll be down to half a heart... and scapular triggers giving you the soul heart back instantly. (remember to leave and come back else scapular won't work).
-also remember sharp plug only works on a completely empty charge... on later floors, don't do something silly like clear a single room to see what's there and give yourself 1/6 charges when you planned on using the infinite trick.
-if you use sharp plug with 2 hearts, you die. From what I can tell, you need to use it with 2.5 hearts to start, or .5 hearts + soul heart for the infinite trick.