I checked online and many people discuss of what is the converted mana cost of cards like Far / Away when they are on the stack but give no answer to what is the CMC when they are in hand. Gatherer treats them as two separate cards with two different CMC.
Option 1 is correct.
While on the stack, the "spells" CMC is that of the upper right corner of the Spell. while on the stack, Far / Away has the CMC of the half you cast (Far or Away). If you have used Fuse, and cast both parts, both halves are on the stack separately, and will each have a CMC equal to the total of the mana in the upper right corner of that spell.
i.e.: The spells are separate while on the stack and have different CMC based on the spells CMC, while the card has a CMC equal to the total mana for both spells written on the card.
Okay... that all may be wrong.
To answer the question best, you should lok at the Gatherer site for the card.
4/15/2013 - In every zone except the stack, split cards have two sets of characteristics and two converted mana costs. If anything needs information about a split card not on the stack, it will get two values.
4/15/2013 - To cast a fused split spell, pay both of its mana costs. While the spell is on the stack, its converted mana cost is the total amount of mana in both costs.
4/15/2013 - When resolving a fused split spell with multiple targets, treat it as you would any spell with multiple targets. If all targets are illegal when the spell tries to resolve, the spell is countered and none of its effects happen. If at least one target is still legal at that time, the spell resolves, but an illegal target cant perform any actions or have any actions performed on it.
Yeah I think it'd work like the old split cards. If one half had a CMC of 2 or lower, you could Imprint it onto the Scepter and choose to cast the other half if you wanted when you used the Scepter.
None of the options laid out in the original post are correct. Far / Away can be imprinted on an Isochron Scepter because it's an instant with CMC 2 or less (the card has both CMC 2 and CMC 3). When you activate the Scepter you choose either half of the card to cast, because that's what you always do when casting a spell from a split card. You're not allowed to Fuse it because you're not casting it from your hand.
Aah nice catch. I didn't see the part about fuse only working from your hand.
To make this clear, yes you can imprint it on to Isochron Scepter , because Far / Away Has two converted mana costs, 2 and 3, unless it is on the stack. Since it will not be on the stack when using this ability, then Far / Away can be imprinted using that ruling.
However, because Far / Away is not cast from the hand when using Isochron Scepter 's effect, and rather is cast from exile (or from nowhere), you will not be able to fuse both halves of the card. You then can only cast one side or the other.
Rulings used/references: http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=369042
4/15/2013 In every zone except the stack, split cards have two sets of characteristics and two converted mana costs. If anything needs information about a split card not on the stack, it will get two values.
4/15/2013 If youre casting a split card with fuse from any zone other than your hand, you cant cast both halves. Youll only be able to cast one half or the other.
12/1/2004 If the copied card is a split card, you may choose to cast either side of the split card, but not both. The split cards Fire/Ice , Illusion/Reality , Night/Day , Stand/Deliver , and Wax/Wane all have at least one side with converted mana cost 2 or less. (they did forget to mention Far / Away as one of the cards, but it does have one side with CMC 2 or less)