Copy edited values before they are edited - google-apps-script

Question

I'm trying to setup a daily report that will send me an email with only the edited rows from a sheet, but also including the old values before they were edited.
I wrote the following script, where when the specified range is edited, the whole row is transferred to another tab called "new_values".
function onEdit_inRange(e,sheetName,sheetRange){
var sh=e.range.getSheet();
if(sh.getName()===sheetName){
var range = SpreadsheetApp.getActiveSheet().getRange(sheetRange);
var xy=[e.range.getColumn(),e.range.getRow()];
if (xy[0]>=range.getColumn() && xy[0]<=range.getLastColumn() && xy[1]>=range.getRow() && xy[1]<=range.getLastRow()) {
return e.range;
}
}
return false;
}
function onEdit(e){
var range=0;
if((range=onEdit_inRange(e,'sheet','M6:O'))){
// SpreadsheetApp.getUi().alert('You Edited a Cell INSIDE the Range!');
} else if ((range=onEdit_inRange(e,'sheet','Q6:Q'))) {
// SpreadsheetApp.getUi().alert('You Edited a Cell INSIDE the Range!');
}
var ss = e.range.getSheet();
//ss.getRange(e.range.getRow(),49) //set timestamp in column 49
//.setValue(new Date()); // Set time of edit in "G"
var appendSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('new_values');
var archiveLastRow = appendSheet.getLastRow();
Logger.log(archiveLastRow);
var archiveAppendRange = "new_values!" + (appendSheet.getLastRow() + 1) + ":" + (appendSheet.getLastRow() + 1);
Logger.log(archiveAppendRange);
var destRange = ss.getRange(archiveAppendRange);
Logger.log(destRange);
var sourceDataValues = ss.getRange(range.getRow(),1,1,49).copyTo(destRange);
Logger.log(sourceDataValues);
}
What I can't manage to do is to make this script to also copy the old values, when they are edited, and move them to another separate tab (called "old_values").
How can I copy the old value, when cells are edited in the same way I do the new values?
My plan is that I'll merge both tables and send over email.
Here's an example spreadsheet with my code: https://docs.google.com/spreadsheets/d/1xzyVD7ElA0FMVC8sta6beDJCIwOQEMRqjhF5eW4mExI/copy