Samsung Galaxy Tab — V3 sound control (.apk)

For my V3 sound module I need to d/l an Android App, called " V3 sound control " I thought to use my old Samsung Galaxy GT-P5110 tablet. Unfortunately it has only Android 4.3, but I flashed it with Lollipop cm-13.0-20160222-2140-UNOFFICIAL ROM and now has OS 6.0.1.

Problem: I am still unable to download " V3 sound control " from Google Play store to my old Galaxy Tab!!  - I deleted Google Play store's cache, but nothing helps. I guess the Google Play store refers to my old model Samsung Galaxy GT-P5110 with Android 4.3 and doesn't allow the download of the App?? - How to overcome it?
I found and downloaded " V3 sound control " via Google search to my laptop desktop, then emailed it to my Tab, adjusted Security (to allow from unknown sources...), but my Galaxy did everything to prevent the download.
I scanned the App with my Eset AntiVirus and it was O.K. What to do?
Thank you in advance for your expert help.
Warm Regards, from young pensioner (78) Joh in Townsville, Qld

— modified on Aug 19, 2020, 3:09:53 PM