I have made few more investigation
it seems that
"Last update" = last user/client post
"Last response" = last agent post
But in my understanding the "Last update" should mean any change maked in this ticket.
So my question is in Problem #5:
Whether in osTicket Queue, can be added column which is showing date of any kind/type change in the ticket ?
To be more precice:
I mean any kind of activity which update Ticket state (user/client post, agent post, internal note added, status changed, ticket transfered to department, ticket assigned to teams, ticket assigned to agent, ticket was edited, colaborators added .... just date of the last activity/change notified in this ticket).
??