Show screen every five or six hours

[Still-learning (1-2-3-4...)]

have you tested this ? it will work(timer) even the app is closed… here as demo 5 min is used. also it will start when button clicked. but you can design when screen initialize set timer to run

Clock remains active when changing screen

try split the vaue at spaces and use select list item list index 3 and 4 alone… simple try like this (modified as per your requirement) [blocks(11)]