Good GTD/todo/tasks app I am looking for a free task management application that has the following:
- Reminders for tasks that can be snoozed (like native reminders app)
- Grouping tasks/Adding subtasks
- UI showing tasks per day/week
- Prioritize task   

I tried Wunderlist and Todoist. Wunderlist has a very nice interface but can not snooze tasks. Todoist also is missing time setting per task.
Anydo seems not working properly. Sometimes I get a popup others not.
What can you recommend?  

Update:
I have checked the apps in the linked post. They are not meeting my requirement. None offers snooze
I like Clear. 

It has reminders that can be snoozed. The snooze time is not optional (unlike the default Reminders app). When you snooze, it simply snoozes for 15 minutes. 

You can create any number of categories under which to put tasks. 

You can very easily prioritize tasks. 

It doesn't really have a "today" or "this week" view except as a widget in Notification Center. 

The UI is unbelievably easy and efficient to use.