The preset time is not binding, you can always start a new task earlier or later. The timer is designed more like an alarm clock (it also does get recognised as one by Android). It will sound an alarm at the end of your specified time and 5 minutes after so that you don’t forget to set a new timer.
I like timeto.me (android). It is designed to log the whole day. It doesn’t seem to support tags, but the checklists might be something similar (?). It doesn’t support exporting to a CSV, but it supports backups and they are in JSON format, so it’s probably good enough.
It’s a relatively new project and visually iOS-leaning, but it’s the best one I found for specifically this problem.
I track my app usage with usageDirect. It displays the usage time of all apps and compiles the data into several graphs.
The best app for limiting apps I found is TimeLimit.io. You can use it for your own device, but it also supports limiting and controlling other devices, e.g. your children’s.
Both apps can be found on F-Droid.
The founder is a billionaire Eron Wolf and he funds the projects: https://m.youtube.com/watch?v=cwz2iZwYpgg&t=950
(https://futo.org/what-is-futo/)