Charred Foyer
Enchantment — Room
At the beginning of your upkeep, exile the top card of your library. You may play it this turn.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)
Warped Space
Enchantment — Room
Once each turn, you may pay 
rather than pay the mana cost for a spell you cast from exile.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)
Oliver Barrett
Rulings
If you cast a spell for an alternative cost of {0}, you can't pay any other alternative costs. You can, however, pay additional costs, such as kicker. If the card has any mandatory additional costs, you must pay those.
(wotc • 2024-09-20)
You pay all costs and follow all timing rules for cards played with the permission granted by Charred Foyer's ability. For example, if the exiled card is a land card, you may play it only during your main phase while the stack is empty.
(wotc • 2024-09-20)
Rulings
If you cast a spell for an alternative cost of {0}, you can't pay any other alternative costs. You can, however, pay additional costs, such as kicker. If the card has any mandatory additional costs, you must pay those.
(wotc • 2024-09-20)
You pay all costs and follow all timing rules for cards played with the permission granted by Charred Foyer's ability. For example, if the exiled card is a land card, you may play it only during your main phase while the stack is empty.
(wotc • 2024-09-20)