Q1. Password prompt does not come up 

[issue] Password prompt does not come up when opening excel(password locked) 2007 spreadsheet 

https://answers.microsoft.com/en-us/msoffice/forum/all/password-prompt-does-not-come-up-when-opening/d1504aab-baa3-4bfb-9bf9-417271d96d56 

[solution] install  Office 2007 sp3  

https://drive.google.com/file/d/1LWh47UDGnuo3TrPnC91fn4-a7ixE2_D_/view?usp=sharing  <- download

 Q2. How to open Excel files in separate windows and multiple instance 

1. Open regedit (win+R, regedit)

2. Browse to HKEY_CLASSES_ROOT/Excel.Sheet.8/shell/Open/command     *.xls

3. In the tab on the right:

Right click on (Default), select Modify..., append a space followed by "%1" (including quotes)

"C:\Program Files (x86)\Microsoft Office\Office12\EXCEL.EXE" /e "%1"

Rename command into command2

4. In the tab on the left:

Just below the command folder

Rename ddeexec into ddeexec2

Browse to HKEY_CLASSES_ROOT/Excel.Sheet.12/shell/Open/command   *.xlsx

Repeat step 3 and 4

Browse to HKEY_CLASSES_ROOT/Excel.CSV/shell/Open/command    *.csv

Repeat step 3 and 4