How does this work?

[MacDad_TN]

Can somebody please explain to me how the following interactions work?  I've looked in every searchable rules database to try and figure this out.

1.) How does Fork (or Twincast) work with Skeletal Scrying?  For example, if my opponent casts skeletal scrying for 3 and I respond with Fork, do I have to remove 3 cards from my graveyard? Do I lose 3 life?  Do I have to do both? 

2.) Same question, but with Tinker.  Do I have to sacrifice an artifact?

Could somebody please explain both of these situations?

Thank you.

[Ivantheterrible]

The cost have been payed already you are mearly copiying the spell so in both situations no you do not have to pay the cost.

[Daniel_112]

For the scrying, you still have to lose life equal to X

[Nibble]

To be a little more in-depth, any spell on the stack has already had its costs paid in full and all choices made, so essentially the object on the stack is just an effect waiting to happen. A Tinker on the stack, for instance, might as well not have the sacrifice an artifact clause on it at all, because it's already been paid and is not part of the effect. Copying a Tinker will give you a copy of the effect, and you won't need to pay the artifact cost.

Also, as was said above, the graveyard removal is part of the cost for Scrying, so you won't have to worry about that, but the life loss is part of the effect. You'll still lose X life.