Hi @nameisnani 

You can use a combination of a Before-Update Business Rule and a UI Policy for your requirement.

1: Create the Business Rule (Auto-Update State)

• Navigate to: System Definition > Business Rules and click New.
• Name: Auto-update to In Progress on Reassignment
• Table: Incident
• When: Before
• Update: Checked
• Condition Tab: State is On Hold AND [Assignment group changes OR Assigned to changes]

(function executeRule(current, previous /*null when async*/) {

        current.state = 2; // Set State to In Progress

})(current, previous);

 2.Create an onChange Client Script

• Navigate to System Definition > Client Scripts and click New
• Fill in the following fields:
1. Name: Make Work Notes Mandatory on Assignment Change
2. Table: incident 
3. Type: onChange
4. Field name: assignment_group

function onChange(control, oldValue, newValue, isLoading, isTemplate) {

   if (isLoading || newValue === '' || oldValue === newValue) {

      return;

   }  

      g_form.setMandatory('work_notes', true);

}

3: Create a onChange Client Script for "Assigned to"

• Name: Make Work Notes Mandatory on Assignee Change
• Table: incident 
• Type: onChange
• Field name: assigned_to

function onChange(control, oldValue, newValue, isLoading, isTemplate) {

   if (isLoading || newValue === '' || oldValue === newValue) {

      return;

   }  

   g_form.setMandatory('work_notes', true);

}