My opponent controls Goblin Guide and attacks me. My top card is Valakut Awakening facing spell-side up. Does it go into my hand?
Second question, let's say in a tournament I register my deck with Valakut Awakening facing up, but later learn that I'll be facing a lot of Goblin Guide in the future, can I switch the side of my Modal Double-Faced Cards in my deck whenever I please? Or only in-between matches when Sideboarding... or must I always have the registered side as the face-up side evertime? Or is it that Valakut Awakening is the official front-facing card, and thus is read as such when in any zone other than the battlefield?
Sometimes I'll have Valakut Stoneforge on the field, and shuffle it into my deck when the game is over. Can I get penalized for forgetting to flip it back to Valakut Awakening? Many questions lol.
All MDFC's have a front and back side, and the card is always the front side of it, unless it is played onto the stack/battlefield as the back. The way to know is the symbol in the upper-left corner of the card: the black triangle is the front, and the double white triangles is the back. So in your case, that card is always Valakut Awakening unless you've played it out as Valakut Stoneforge. Similarly, a card like Cragcrown Pathway is the front, and Timbercrown Pathway is always the back even though they are both lands.
To your actual questions:
1) No, GG just sees a spell, never the back side. This is the reason that modern Charbelcher decks work.
2) No, MDFC's always start in the deck as the front side. The card isValakut Awakening with an option of being a land.
3) Potentially, but as always depends on enforcement level. This seems like a minor thing, and doesn't really affect the game in the same way as leaving in a sideboard card or something similar, but still technically is the wrong card in your deck. If it happens once or twice, you probably just "oops" and flip it quick, but if you keep doing it, or do it on purpose to try and get an advantage, it'll probably catch up with you. In your 2nd question example, if you flipped all your DFC's to the land side, and then insisted you get them off of Goblin Guide triggers, this would probably result in some judge action.
In general, you may insert an opaque sleeve on a double-faced card so that only the back face of that card shows. Nothing in the comprehensive rules or the Magic: The Gathering Tournament Rules disallows this (for sanctioned tournaments, review M.T.R. 3.10). Remember, though, that inserting a sleeve on a double-faced card to show the back face rather than the front face doesn't change how that card is seen by the game, and that any player that can look at a double-faced card can look at both its faces (C.R. 712.2).
For example, a double-faced card in your library or your hand has only the front face's characteristics even if you inserted an opaque sleeve on that card to show only its back face (C.R. 712.4a). Moreover, it's unnecessary to resleeve double-faced cards to change the face they show in between games of a match.
Second question, let's say in a tournament I register my deck with Valakut Awakening facing up, but later learn that I'll be facing a lot of Goblin Guide in the future, can I switch the side of my Modal Double-Faced Cards in my deck whenever I please? Or only in-between matches when Sideboarding... or must I always have the registered side as the face-up side evertime? Or is it that Valakut Awakening is the official front-facing card, and thus is read as such when in any zone other than the battlefield?
Sometimes I'll have Valakut Stoneforge on the field, and shuffle it into my deck when the game is over. Can I get penalized for forgetting to flip it back to Valakut Awakening? Many questions lol.
Thanks alot in advance!
To your actual questions:
1) No, GG just sees a spell, never the back side. This is the reason that modern Charbelcher decks work.
2) No, MDFC's always start in the deck as the front side. The card is Valakut Awakening with an option of being a land.
3) Potentially, but as always depends on enforcement level. This seems like a minor thing, and doesn't really affect the game in the same way as leaving in a sideboard card or something similar, but still technically is the wrong card in your deck. If it happens once or twice, you probably just "oops" and flip it quick, but if you keep doing it, or do it on purpose to try and get an advantage, it'll probably catch up with you. In your 2nd question example, if you flipped all your DFC's to the land side, and then insisted you get them off of Goblin Guide triggers, this would probably result in some judge action.
In general, you may insert an opaque sleeve on a double-faced card so that only the back face of that card shows. Nothing in the comprehensive rules or the Magic: The Gathering Tournament Rules disallows this (for sanctioned tournaments, review M.T.R. 3.10). Remember, though, that inserting a sleeve on a double-faced card to show the back face rather than the front face doesn't change how that card is seen by the game, and that any player that can look at a double-faced card can look at both its faces (C.R. 712.2).
For example, a double-faced card in your library or your hand has only the front face's characteristics even if you inserted an opaque sleeve on that card to show only its back face (C.R. 712.4a). Moreover, it's unnecessary to resleeve double-faced cards to change the face they show in between games of a match.
EDIT (Aug. 2): Edit rule citation.