To change the existing file format type from CSV to JSON, the recommended way is to use the ALTER FILE FORMAT command with the SET TYPE=JSON clause. This alters the file format specification to use JSON instead of CSV. Reference: Based on my internal knowledge as of 2021.

To ensure that additional multi-clusters are resumed with no delay, a virtual warehouse should be configured to a size larger than generally required. This configuration allows for immediate availability of additional resources when needed, without waiting for new clusters to start up

In Snowflake streams, the METADATASACTION column indicates the type of data manipulation operation that has occurred. The possible values include INSERT and DELETE.
INSERT: Indicates that a new row has been inserted into the table.
DELETE: Indicates that a row has been deleted from the table.
Reference:
Snowflake Documentation: Change Data Capture (CDC) with Streams
Snowflake Documentation: Stream Data Capture

The account usage views in Snowflake provide historical usage data about the Snowflake account, and they retain this data for a period of up to 1 year. These views include information about dropped objects, enabling audit and tracking activities. On the other hand, information schema views provide metadata about database objects currently in use, such as tables and views, but do not include dropped objects. The retention of data in information schema views varies, but it is generally shorter than the retention for account usage views, ranging from 7 days to a maximum of 6 months, depending on the specific view.
Reference: Snowflake Documentation on Account Usage and Information Schema

In Snowflake's data sharing model, any full Snowflake account can both provide and consume shared data. Additionally, the data consumer pays only for the compute resources used to query the shared data. No actual data is copied or transferred between accounts, and shared data does not take up any storage in a consumer account, so the consumer does not pay for data storage1.
Reference = Introduction to Secure Data Sharing | Snowflake Documentation