2 questions for a datapack

got 2 questions: 1. how do u make it so a custom command runs multiple mc commands? like /customcommand will run the /title command multiple times or sumn? 2. can u make commands happen in a specific time? let's say i made a revival feature in hardcore minecraft, but they will only be revived for 15 mins. how would I make it so they're set back to spectator in 15 mins time?