Which alter command below may affect the availability of column with respect to time travel?

You will be using a multi cluster warehouse. You will statically control the available resources (i.e. servers) and you have large numbers of concurrent user sessions and/or queries and the numbers do not fluctuate significantly.
Which mode will you use for the warehouse?

Materialized views are recommended for all of the scenarios except

Which command below will only copy the table structure from the existing table to the new table?

You want to automatically delete the files from stage after a successful load using the COPY INTO command.
What will be recommended approach for deletion?