MTG Salvation

No, to both. Flash has you sacrifice immediately as it resolves, so the creature won't be around long enough to be declared as a blocker. And when you cast a creature for its evoke cost, it will be sacrificed when the evoke triggered ability resolves. So, likewise, it won't stick around long enough to be declared as a blocker.

Also, note that you have to put a creature onto the battlefield *before* the declare blockers step if you want to declare it as a blocker.

In every zone other than the stack, a split card’s CMC is equal to the CMC of both halves combined.

Yes, you can cast those instants during your end step. Assuming they all targeted a creature you control, those instants will return to your hand at the beginning of your opponent’s end step.

1. If you cast the Far half of Far//Away, the CMC of the spell on the stack is 2.

2. Mulldrifter’s CMC is 5, even when cast for its evoke cost. Likewise, an overloaded spell’s CMC is the same as it would be if you cast the card for its normal cost. A card’s converted mana cost is determined by the mana symbols in the card’s upper right-hand corner, even if that’s not the amount of mana you’re actually paying to cast it for whatever reason.

When an object changes zones, any counters that were on it are removed. When the land returns to the battlefield, it is considered a new object with no memory of, or relation to its previous existence. The land won't remember that it was animated earlier, and will return as just a land without any counters.

Yes, Dread Presence will see a Swamp entering the battlefield in this case.

No, you cannot. You are unable to combine costs like that. If you sacrifice Dawntreader Elk to activate its ability, you would be unable to sacrifice it for the Scourge's ability, because it's already in the graveyard by the time you want to use the Scourge's ability.

You'll lose the game, because you hit 0 life at the same time as your slivers are dealt damage. The next time state-based actions are checked, which is before the slivers' abilities go on the stack, you lose the game and those triggers never get a chance to go on the stack.

After the encoded Nightscape Battlemage deals combat damage to a player, you'll indeed have three total Battlemages: the original, the copy from the initial cast of Stolen Identity, and a second copy from the ciphered Stolen Identity.

No, the copies of Battlemage won't trigger any of its abilities, because you didn't pay the kicker cost for them, nor are you able to pay -- kicker is an additional cost paid when casting a spell, and the copies of Battlemage were not cast.

To answer your other question, if you cast Lightning Bolt on Liliana and your opponent sacrifices a nontoken creature in response, then Liliana will be exiled and returned tranformed before your bolt resolves. And since the object you targeted no longer exists, your bolt will be countered on resolution for having no legal target.

Gruul Spellbreaker enters the battlefield with a +1/+1 counter, which means it will cause Kiora's ability to trigger.

It doesn't sound right because it isn't right. Lion's Eye Diamond's mana ability can only be used whenever you could cast an instant, which means you need to have priority. LED's Oracle rules text and old Gatherer ruling back this up:

Sacrifice Lion's Eye Diamond, Discard your hand: Add three mana of any one color to your mana pool. Activate this ability only any time you could cast an instant.

10/4/2004 The ability is a mana ability, so it is activated and resolves as a mana ability, but it can only be activated at times when you can cast an Instant. Yes, this is a bit weird.

Normally, you can activate mana abilities at times you don't have priority but need to pay mana, such as during the resolution of a spell/ability that asks for mana payment, or in the process of casting a spell. However, LED's last sentence means that you cannot activate its mana ability during those times, as no player has priority at those times (which means, among other things, that you cannot cast an instant at those times).

Edit - Oh wait, I see your friend is attempting to use LED after announcing the spell, but before it has been cast, as though that's a thing. Most assuredly, it is not, and a simple quote from the Comprehensive Rules dispels that misconception:

601.2. To cast a spell is to take it from where it is (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. Casting a spell follows the steps listed below, in order. If, at any point during the casting of a spell, a player is unable to comply with any of the steps listed below, the casting of the spell is illegal; the game returns to the moment before that spell started to be cast (see rule 717, "Handling Illegal Actions"). Announcements and payments can't be altered after they've been made.

601.2a. The player announces that he or she is casting the spell. That card (or that copy of a card) moves from where it is to the stack. It becomes the topmost object on the stack. It has all the characteristics of the card (or the copy of a card) associated with it, and that player becomes its controller. The spell remains on the stack until it's countered, it resolves, or an effect moves it elsewhere.

As you can see, 601.2a outlines that announcing that you're casting a spell is in fact the first step of casting a spell; you can't "announce you're casting, activate LED, and then actually cast", because the rules don't work like that.

Yes. From Karmic Justice's Gatherer rules entries:

10/4/2004 If an opponent destroys Karmic Justice, it will trigger on its own destruction.

Nothing in Volcanic Offering's text prohibits an opponent from targeting the same nonbasic land that you selected. The only targeting restriction is "target nonbasic land you don't control". Your opponent is free to target the same nonbasic land, should they choose.

You'll put a +1/+1 counter on each creature you control three times. The Gatherer rulings entry for Tempt with Glory helps clarify this:

10/17/2013: After each opponent has decided, the effect happens simultaneously for each one who accepted the offer. Then, the effect happens again for you a number of times equal to the number of opponents who accepted.

So, with 3 opponents choosing to put a +1/+1 counter on each creature you control, Tempt with Glory will end up placing 8 +1/+1 counters on each of your creatures (2 for the first instruction, then 2 more, 2 more, and 2 more).

Edit - I will say that my answer is entirely based on the Gatherer ruling's wording, which I understand is quite a flimsy foothold. I was hoping that our resident Wizards NetRep might be able to shed some light on this. Holding on for more insight!