Order of Execution Rules:
Step 1: Original record is loaded from the database.
Step 2: Field-level validations are performed, including maximum field lengths.
Step 3: Old values are overwritten with new record values.
Step 4: JavaScript validation runs in the browser.
References:Order of Execution Rules:https://developer.salesforce.com/docs/atlas.en-us.238.0.
salesforce_appdevelopment.meta/salesforce_appdevelopment/apex_triggers_order_of_execution.htm