Explanation
Earliest Start Permitted is a field on the Service Appointment object that defines the earliest date and time that a service appointment can start[222]. Due Date is a field on the Service Appointment object that defines the latest date and time that a service appointment must be completed by[223]. Using Earliest Start Permitted and Due Date fields on Service Appointments would help ensure that they are completed within the agreed upon Service Level Agreement (SLA) with Universal Containers' customers by setting the boundaries for when a service appointment can start and finish according to the SLA terms[224]. Actual Start and Actual End are fields on the Service Appointment object that capture the actual date and time that a service appointment started and ended[225]. Using Actual Start and Actual End fields on Service Appointments would not help ensure that they are completed within the agreed upon SLA with Universal Containers' customers because they are recorded after the service appointment is performed and do not enforce any SLA terms. Arrival Window Start and Arrival Window End are fields on the Service Appointment object that define the expected date and time range that a resource will arrive at a service appointment[226]. Using Arrival Window Start and Arrival Window End fields on Service Appointments would not help ensure that they are completed within the agreed upon SLA with Universal Containers' customers because they only indicate when a resource will arrive and do not enforce any SLA terms. Scheduled Start and Scheduled End are fields on the Service Appointment object that define the planned date and time range that a service appointment will take place[227]. Using Scheduled Start and Scheduled End fields on Service Appointments would not help ensure that they are completed within the agreed upon SLA with Universal Containers' customers because they only indicate when a service appointment is scheduled and do not enforce any SLA terms. References:
https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_objects_serviceappointment.htm
https://help.salesforce.com/s/articleView?id=sf.fs_sla_overview.htm&type=5

Explanation
Gantt Palettes allow the dispatcher to color code service appointments based on any field value, such as revenue or priority. References: https://help.salesforce.com/s/articleView?id=sf.fs_gantt_palettes.htm&type=5

This option allows the Resource Skill to expire when the certification expires, and prevents the resource from being scheduled for jobs that require that skill. References:
https://help.salesforce.com/s/articleView?id=sf.fs_resource_skills.htm&type=5