Dirgur Focusmage // Braingeyser

If an effect instructs you to choose a card name, you may choose the alternative prepare spell's name. Consider only the alternative characteristics to determine whether that is an appropriate name to choose.

Creating a copy of a creature's prepare spell in exile ignores copy exceptions applied to that creature that would affect the copiable values of that spell. For example, say a player casts Croaking Counterpart (a sorcery that says "Create a token that's a copy of target non-Frog creature, except it's a 1/1 green Frog.") targeting Goblin Glasswright. The token copy of Goblin Glasswright will enter prepared as a 1/1 green Frog creature, but the copy of Craft with Pride in exile will still be a red sorcery. The copy of Craft with Pride won't be green, a creature, or a Frog, and it won't have power or toughness.

Only the current controller of a prepared creature can cast the copy of its prepare spell in exile. It doesn't matter who owns that creature or who controlled it when it became prepared.

Dirgur Focusmage's last ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack without resolving.

While copies of spells in zones other than the stack cease to exist when state-based actions are checked, this does not apply to copies of prepare spells in exile that were created as a creature became prepared.

If a prepared creature stops being a creature, it will still be prepared, and the copy of its prepare spell will remain in exile. That permanent's controller will still be able to cast it. The same is true if a prepared creature becomes a copy of something else, even if it's then a permanent without a prepare spell.