'Edit Only' Mode for Assignee/Collaborator(s)

Hi Aymeric, Weekplan really help get things done. Thanks a lot.

My 1st question is - how can I allow others only to edit/comment/complete tasks and not delete them?

2. Can I also show member(s) the tasks assigned to him/her only and hide other tasks assigned to someone else in the same work-space?

Please advise.