Alerting on memory use and instance crash

Hi Experts,

It's postgres version 16. I have two questions on alerting as below.

1)If we want to have alerting on any node/instance that gets crashed :- In
other databases like Oracle the catalog Views like "GV$Instance" used to
give information on whether the instances are currently active/down or not.
But in postgres it seems all the pg_* views are instance specific and are
not showing information on the global/cluster level but are restricted to
instance level only. So is there any other way to query the pg_* views to
have alerts on the specific instance crash?
2)Is there a way to fetch the data from pg_* view to highlight the specific
connection/session/sqls which is using high memory in postgres?

Appreciate your guidance.

Regards
Sud