If i have Braids, Arisen Nightmare and Strionic resonator in play. At the beginning of my end step, if i copy the ability on stack i need sacrifice 1 permanent for each resolve or the sacrifice was be paid and i just copy the "good" part of it?
You can cast Visions off Citadel because it gives you a payable cost; you are not trying to use 2 alternate costs there. You are *only* using Citadel's cost to cast the Visions. It doesn't matter that Visions normally has an unpayable cost because you aren't paying that.
In the case of Morph, you are trying to use both the Morph cost (turn it face down, cast for 3) and Citadel (pay 0 life now that it is face down). And you can't combine alternate costs.
So in that case I would have to pay 3 life or can't cast using Citadel?
Not in this case, no. Both the cost from the Citadel and Morph are alternate costs and you can only use 1 alternate cost when casting a spell. And, in this case, only one cost lets you cast it from the top of your library.
Accordig to the rule 702.36c, to cast a card using its morph ability, turn it face down. It becomes a 2/2 face-down creature card with no text, no name, no subtypes, and no mana cost. Any effects or prohibitions that would apply to casting a card with these characteristics (and not the face-up card’s characteristics) are applied to casting this card.
With Bolas's Citadel in play, Can i pay 0 to cast a morph card from top of library?
So in that case I would have to pay 3 life or can't cast using Citadel?
Okay, but Bolas's Citadel doesn't allow me to use Ancestral Vision for 0 life even though it has an alternative cost?
Why i can't use this same logic with morph?
With Bolas's Citadel in play, Can i pay 0 to cast a morph card from top of library?