External stages can be altered and dropped in Snowflake. An external stage points to an external location, such as an S3 bucket, where data files are stored. Users can modify the stage's definition or drop it entirely if it's no longer needed. This is in contrast to table stages, which are tied to specific tables and cannot be altered or dropped independently.
References:
* [COF-C02] SnowPro Core Certification Exam Study Guide
* Snowflake Documentation on Stages1

* Object-level access control is available in all Snowflake editions.
* This feature allows administrators to grant and revoke permissions on specific objects (e.g., tables, schemas, databases) to control access at a granular level.
* Other features like data masking policies and customer-managed encryption keys are available only in higher Snowflake editions.
References:
* Snowflake Documentation: Object-Level Access Control
* Snowflake Editions Comparison

Explanation
External functions are user-defined functions that are stored and executed outside of Snowflake.
External functions make it easier to access external API services such as geocoders, machine learning models, and other custom code running outside of Snowflake. This feature eliminates the need to export and reimport data when using third-party services, significantly simplifying your data pipelines.
https://docs.snowflake.com/en/sql-reference/external-functions.html#:~:text=External%20functions%20are%20u

Micro-partitioning is a Snowflake function that is maintained separately from the data and supports features such as Time Travel, Secure Data Sharing, and pruning. It allows Snowflake to efficiently manage and query large datasets by organizing them into micro-partitions1.

Snowflake implements Discretionary Access Control (DAC) by using a role-based access control model. In this model, access privileges are not directly assigned to individual objects or users but are encapsulated within roles. These roles are then assigned to users, effectively granting them the access privileges contained within the role. This approach allows for granular control over database access, making it easier to manage permissions in a scalable and flexible manner.
Reference: Snowflake Documentation on Access Control