When you take the Magic (Identify) action as a reaction with a magus spell and succeed, you can prepare the spell identified and count it as a magus spell as part of the same reaction, provided it is of a level you can prepare, without counting against the number of magus spells you have prepared. The spell remains prepared until you use this feature again or you finish a long rest.
When you take the Spellcast action while hidden and miss, you don't lose the hidden condition. Moreover, if you take the Attack action with an attuned weapon or the Magic (Spellcast Attack) action with a magus spell, you can take an action become invisible until the end of the turn.
When a creature takes the Magic (Spellcast) action against you, you can take take the Magic action as a reaction to make an Intelligence (Sleight of Hand) check against the creature's spell save DC. On a successful check, the spell fails and you regain one expended level 1 spell slot.
Once you use this feature, you can't use it again until you finish a short rest, unless you expend X mana points.
When a creature that you can see takes the Magic (Spellcast) action, you can take the Magic (Identify) action as a reaction to cause the creature to make a saving throw using its spellcasting ability against your spell save DC. On a failed save, the action fails, the spell slot is expended, and the creature can't cast that spell again until it finishes a long rest.
Moreover, as part of the same reaction, if the creature fails the saving throw, you can prepare the spell as a magus spell, provided you have a spell slot of the spell's level. The spell remains prepared until you use this feature again. Alternatively, you can take the Magic action at the start of your next turn to cast the spell at its lowest level using your spellcasting ability, without providing a spell slot or spell components.
Once you use this feature, you can't use it again until you finish a long rest, unless you expend X mana points.