Tablet W10 hidden keyboard and osk.exe

Hello all,
It seems I've got problem with keyboard on tablet which runs with Windows 10. The tablet
has no keyboard and no mouse.
I want to lock tablet only for one application, which has to use keyboard, unfortunately.
When I set up tablet W10 into "desktop mode" after "Secure Lockdown" start the keyboard icon
disappears with "task bar".
When I set up tablet W10 into "tablet mode" after "Secure Lockdown" start there is only clean white
"task bar" without keyboard icon.
So I've tried to install "Inteset on-screen keyboard helper" sw. When I start
"Inteset on-screen keyboard helper.exe" I get error message with information that there isn't
".NET Framework 3.5." in Windows 10 operating system....
By the way, is the osk.exe accurate and right way?

Could you give me some advice, how to solve issue above.
Thank you very much for purposeful solution.
Enjoy your day.
Peter B.

You should be able to use the Windows 10 virtual keyboard. If in Tablet Mode, the keyboard will pop up when in an input field. You shouldn't need the icon in the Taskbar