statement 1 i=if there is no cycle in resource allocation graph then it means that there is no circular wait so one of the necessary condition for deadlock is not satisfy that's why there will be no deadlock.
statement 2=if there is cycle in resource allocation graph if it is of single instance type then it satisfy all the condition for deadlock i.e
mutual exclusion,circular wait,hold and wait,no preemption so deadlock will occur.
statement 3=if there is cycle in multi instance resource type then it is not necessary that deadlock will occur because sometimes it may happen that one of the resource will be available for the other process.
so all the statement is correct.