Helpdesk software with configuration

Requirements: An open sourced (preferred) help desk software which can do following

1. Any email sends to primary email either create a new task or ticket or amends the existing tasks
2. New tasks either get auto assigned or manually assigned
3. Each task has one owner and multiple watchers (who need to know but are not responsible for actions)
4. Permissions based on domains and group memberships.
5. One user can have more than one group membership across multiple domains
6. Dashboard – information available based on domain and group membership
7. Some mechanism for notifications;
a. A new task or ticket is created
b. Tickets are not updated for certain period based on SLA defined Identify the tickets which failed to meet the SLAs and also identify the user who is assigned to such tickets
8. Available on desktop and as a mobile app
9. Available to external user and customers

Note:
1. 1. Commercial application which have cost per user, like Jira, Service Desk Plus etc. are last resort. First effort to get free open source (iTOP, FreeScout etc. ) or an application with minimal cost
2. A documented setup configured for demo is needed with non production domain before it is accepted.