Hi friends
I have to work on batch apex code .
I have mentioned the ​​entire code.

The scenario is : ​If sales lead does not follow the contacts in 2 days then it is assigned to another user.​
In contact object, custom field called days_since_last_activity. If greater than 2 then records are assigned to another user and email sent.
This is my understanding.

global class UpdateAllContacts implements Database.Batchable<sObject>
 {
   
     //This is the query that is passed to the execute method.  It queries all of the Contacts who have passed the protected period.
    
     String query = 'Select Id, OwnerId FROM Contact WHERE Days_Since_Last_Activity__c > 2';
   
     global database.queryLocator start(Database.BatchableContext BC)
     {
        return database.getQueryLocator(query);
     } //close start method
   
     global void execute(Database.BatchableContext BC, list <Contact> scope)
     {
   
        List <Task> taskList = new List<Task>();
     // Iterate through the whole query of Contacts.
     // Create a Task that's associated with each Contact.  This resets the Days Since Last Activity formula field.
     for(Contact c : scope)
     {
               c.OwnerId = '00590000003s0MYAAY';
               Task tsk = new Task();
               tsk.WhoId = c.Id;
               tsk.ActivityDate = System.today();
               tsk.Status = 'Completed';
               tsk.Subject = 'Ownership Transferred';
   
               taskList.add(tsk);
    
    } //close for-loop
   
     try
     {
        insert taskList;
     }
     catch(exception e)
     {
        System.debug('Tasks not inserted: ' + e);
     }
   
     try
    {
        update scope;
     }
     catch (system.dmlexception e)
     {
        System.debug('Scope not updated: ' + e);
     }
   
     } //close execute method
   
   
     global void finish(Database.BatchableContext BC)
     {
   
     AsyncApexJob a = [Select Id, Status, NumberOfErrors, JobItemsProcessed,TotalJobItems, CreatedBy.Email from AsyncApexJob
                       where Id =:BC.getJobId()];
   
     // Create and send an email with the results of the batch.
     Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
   
     mail.setToAddresses(new String[] {a.CreatedBy.Email});
     mail.setReplyTo('batch@mycompany.com');
     mail.setSenderDisplayName('Batch Processing');
     mail.setSubject('Contact Update ' + a.Status);
     mail.setPlainTextBody('The batch apex job processed ' + a.TotalJobItems + ' batches with ' + a.NumberofErrors + ' failures.');
   
     Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
     } //close finish method class
    
} //close global class



global class ScheduleUpdateContacts implements Schedulable
{
    global void execute(SchedulableContext SC)
    {
        UpdateAllContacts uac = new UpdateAllContacts();
       
        database.executebatch(uac);
       
    } //close execute method
   
} //close class

I want to know:
a) If user_A has 1000 contacts under him and he does not follow up in 2 days then how all 1000 records get assigned to another user?
    are we hardcoding the userID
b) are we assigning all 1000 records to single user?
c) ​​​​​​​how do I check if say User_B has been assigned all 1000 records because user_A did not follow since last 2 days?
d) does the system admin transfer ownership to another user:?

please help me out in understandng this.

thanks
meenakshi​​​