Differences between Polling method and Status & Response time as ICMP/SNMP?

Hi All,

I have few questions:

Why we always get notification " You see cached version of resources from.......for few nodes"?

How " Status & response time work as ICMP & SNMP ?

How does SNMP works like there will be any calculations method or how much time it takes to complete the task?

How "SNMP polling method" and " Status and Response time- SNMP" are different?