I want to get alerts before an SLA violation happens. Can I configure this?

Yes, Vtiger CRM gives you an option to configure email alerts that must be sent before an SLA violation happens.
This is how you must configure the alerts in the SLA policy:

When you enable the Alerts checkbox for any priority, you must configure three things:

1. Select the users who must be alerted when the SLA is about to be violated.
2. Enter the time when the email alert has to be sent before the SLA violation.
3. Select an email template to send the alert. These email templates are related to cases or internal tickets based on the type of SLA you are creating. To know more about Email Templates, click here.

You can click the + Add Alert button to add multiple alerts at different time intervals, with the same or different users for the SLA policy.

To know more about SLA Policies, click here.