Which of the following fields are available in both the global /etc/crontab file as well...

The crontab file format consists of six fields: minute, hour, day of month, month, day of week, and command. The user-specific crontab files have the same format as the global /etc/crontab file, except that they do not have the username field. The username field is only present in the system-wide crontab files and specifies which user will run the cron job. The year field is not a valid crontab field and is not supported by cron. References:

Scheduling Cron Jobs with Crontab | Linuxize

Crontab Explained in Linux [With Examples]