Based Picklist Save the record

===========VFPage==============
<apex:page controller="Rahultask">
  <apex:form >
    <apex:pageBlock rendered="{!display}">
      <apex:pageBlockSection >
         <apex:selectList value="{!Names}" label="select Name" size="1">
            <apex:selectOptions value="{!selectName}">
            </apex:selectOptions>
            <apex:actionSupport action="{!change}" event="onchange" />
         </apex:selectList>
      </apex:pageBlockSection>
     </apex:pageBlock>
     <apex:pageBlock rendered="{!display1}" title="ashok" id="pb">
         <apex:pageBlockSection >
             <apex:inputField value="{!obj.Name}"/>
            <apex:inputField value="{!obj.number__c}"/>
            <apex:inputField value="{!obj.ahs__c}"/>
         </apex:pageBlockSection>
         <apex:pageBlockButtons >
            <apex:commandButton value="Save" action="{!Save}"/>
         </apex:pageBlockButtons>
     </apex:pageBlock>
     <apex:pageBlock title="Details" rendered="{!display2}">
        <apex:pageBlockTable value="{!listobj }" var="A">
            <apex:column value="{!A.Name}"/>
           <apex:column value="{!A.number__c}"/>
           <apex:column value="{!A.ahs__c}"/>
        </apex:pageBlockTable>
     </apex:pageBlock>
  </apex:form>
</apex:page>
===========Controller==============
public with sharing class Rahultask {

    public PageReference Save() {
        insert obj;
        display=false;
        display1=false;
        display2=true;
        return null;
    }

   public Rahultask (){
     obj=new NNR__c();
     display=true;
     display1=false;
     display2=false;
   }
    public nnr__c obj{set;get;}
    public PageReference change() {
        display1=true;
        display2 =false;
        return null;
    }
  public boolean display2 { get; set; }
    public boolean display1 { get; set; }
   
    public Boolean display { get; set; }

    public NNR__c listobj {  set; }
   
    public List<NNR__C> getlistobj (){
       List<NNR__c> n= new List<nnr__c> ();
       n=[select name,ahs__c,nnr1__c,number__c from nnr__c where name=:names];
       return n;
    }

    public String ahs { get; set; }

     public String Names {  set; get;}
     public String selectName {set;}
   
     public List<selectoption>  getselectname(){
               List<selectoption> options = new List<selectOption>();
        options.add(new selectOption('','None'));
        for(NNR__c cn:[select id,Name from NNR__c order by Name]){
            options.add(new selectOption(cn.Name,cn.Name));
        }
        return options;

     }
  }