var sheetId = "1pTd5Av3tkKkim_HuKiKCP-Q2L-aONGKAbwAmOb2cdQ8" //Id Sheet  

var formId  = "1vL2D3A2Xq6UQZlOFs4T8N4JQ4CF5Mxi_tmHDIoJu1KY" //Id Form

function myFunction(){

var ss =SpreadsheetApp.openById(sheetId)

var sheet = ss.getSheetByName("Form Responses 1") //Sheet name

var form = FormApp.openById(formId)

//Roll No Short Answer

var data = [...new Set(sheet.getDataRange().getDisplayValues().map(row=> row[1]))].join('|')

var item = form.getItems().filter(item=>item.getTitle() == 'Roll No')[0].asTextItem()

var pattern = `(${data})`

var textval= FormApp.createTextValidation().setHelpText("Already exists in database !!").requireTextDoesNotMatchPattern(pattern).build()

item.setValidation (textval)

//Name Short Answer

var data1 = [...new Set(sheet.getDataRange().getDisplayValues().map(row=> row[2]))].join('|')

var item1 = form.getItems().filter(item=>item.getTitle() == 'Name')[0].asTextItem()

var pattern1 = `(${data1})`

var textval1 = FormApp.createTextValidation().setHelpText("Already exists in database !!").requireTextDoesNotMatchPattern(pattern1).build()

item1.setValidation (textval1)

//Remarks Paragraph

var data2 = [...new Set(sheet.getDataRange().getDisplayValues().map(row=> row[3]))].join('|')

var item2 = form.getItems().filter(item=>item.getTitle() == 'Remarks')[0].asParagraphTextItem()

var pattern2 = `(${data2})`

var textval2 = FormApp.createParagraphTextValidation().setHelpText("Already exists in database !!").requireTextDoesNotMatchPattern(pattern2).build()

item2.setValidation (textval2)

}