could be trigger, could be sql agent job, could be sql agent alert,  could be from another instance monitoring the environment, question is what suits in your environment, only you...

as far as i know, resource governor is configured for local instance, so you might want to configure it on other node(s) as well, test test test test in development...

create stored procedure with execute as ??

you can test by creating/attaching/formatting  a VHD drive in 'Disk Management'  , let us know the results. 

ofcourse

sql server will be up assuming all system databases are on c drive, I would assume database(s) will be in suspect mode (I doubt it will retry to scan databases),...

how about using SQL alerts for notification

USE [msdb]
GO

/****** Object: Alert [Database Role Membership Change]  Script Date: 1/24/2019 4:14:39 PM ******/
EXEC msdb.dbo.sp_add_alert...

To reduce downtime, you could use filegroup backup/restore, but you have to prepare your database for that

try that. 

1) shutdown sql service
2) copy mdf/ldf files somewhere so that you can come back to this point if required
3) start sql server service

run...

try using kill UOW

https://docs.microsoft.com/en-us/sql/t-sql/language-elements/kill-transact-sql?view=sql-server-2016

sys.dm_tran_active_transactions

umm... let it finish 

 KILL 69 WITH STATUSONLY

Transaction rollback in progress. Estimated rollback completion: xx% Estimated time left: xx seconds.

careful with the col  order

create table t1 (c1 int, c2 int, c5 int);
create table t2 (c3 int, c4 int , c6 int);
create table t3 (c1...

see above

1. How can I get the OS and SQL server current patch level information? is it select @@version? or do we have better options?
you may register all your boxes...

SELECT [object_name]
  ,[counter_name]
  ,[instance_name]
  ,[cntr_value]
  ,[cntr_type]
FROM [master].[sys].[dm_os_performance_counters]