How to get inputted value in a RTE field on custom page and submit by REST call in 'Sharepoint hosted app'.

Hi I am facing the three questions below.

1. How to use default RTE in custom page in Sharepoint hosted app.

 I saw the article of Rich text Editor (ribbon based) in a webpart in SharePoint 2013 and tried it. But it did not work well. I guess it needs code-behind setting, however sharepoint hosted app does not support code-behind.

Does anybody know how to do this?

2. In above case, I placed the below code on custom page and tried to get the field's value when submit button was clicked.

<SharePoint:InputFormTextBox ID="rftDefaultValue"
    RichText="true"
    RichTextMode="FullHtml" runat="server"
    TextMode="MultiLine" Rows="5"></SharePoint:InputFormTextBox>

In debugger, the returned value was 'undefined'.

var note = $('#hogehoge').val();

Is it possible to get the RTE value? If yes, please let me know how to do this.

3. I need to submit the RTE value using REST call.

In this article in MSDN, the item creation sample treats single line text field. Does anybody know the sample for RTE?