Does one who sets an alarm to wake up during the last third of the night for supplication and prayer attain the virtue of the Prophet’s ﷺ hadith regarding those who stir in the night, or is that virtue specific to one who wakes up without prior intention?

"Man ta'arra min al-layl" means whoever wakes up at night, which includes those who wake up by themselves or by means of an alarm. It has been reported from the Prophet (peace be upon him) that whoever wakes up at night and recites the specific dhikr: "There is no god but Allah, alone, without partner..." then supplicates, his supplication will be answered. And if he performs ablution and prays, his prayer will be accepted. This dhikr is required from everyone who wakes up at night. The scholars have understood this general meaning and have made it among the Sunnahs for everyone who wakes up in the middle of the night, and among the Sunnahs for waking up to perform Tahajjud.