I cannot complete the Lightning Experience Rollout Specialist Supderbadge. Everytime I tried to complete the Challenge 6 it gives me this error

There was an unexpected error while verifying this challenge. Usually this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: HSMONHBW

What should I do ?

So I am building a Custom Visualforce page in which I have created a custom object say Student. Now I want to search Students using a search box in a visualforce page so that if I click on a student's name it details gets filled shown in the fields below. 

Although I tried doing it with Lookup field which I set up as Mentor for each student but I want the lookup to show student names instead of the mentors

<apex:page standardController="Student__c"   showHeader="false" >
    
 <h1 style="align: center; font-size:x-large">Student Details</h1>
 
 

<apex:form>
        <apex:inputField value="{!Student__c.Mentor__c}"/>
</apex:form>
    <apex:pageBlock>
        <apex:pageBlockSection>
            <h3>Student Name:</h3>
            <h5>Student Class: </h5> 

        </apex:pageBlockSection>
    </apex:pageBlock>


</apex:page>

I have a custom object Student in which I want to give a unique value to Class roll number field. I am creating a trigger for that. Can you please tell me how to achieve the same in Apex. New here

trigger RollCheck on Student__c (before insert) {
    
    List<Student__c> los = new List<Student__c>();
    
    for(Student__c student: trigger.new){
        student = new Student__c(id = student.id);
        
        if(student.Class_Roll_Number__c == null){
            System.debug('Roll Number is already assigned');
        }
        else{
             #This part. Help me figure it out please?


        }
            
    }

}

Hi ,
In lightning i have one requirement, the text field should be hielight with red boarder based on condition ,please help me .

Thanks 
S.Shanmuka