Google Opinion Reward. You get random survey question every now and then and you get Google Play Credit, which can be use on any mobile game. You don't get much but it add up over time. This only work with Android.
Download the app here: https://play.google.com/store/apps/details?id=com.google.android.apps.paidtasks&hl=en
Yup, QooApp would be (one of) the most widely used apk(app) download portals where you can get apks for all kinds of games like T7S, idolmaster starlight stage etc.
https://apps.qoo-app.com/en you can download the .apks that you want directly from here, or download and install qooapp itself and download .apks from within the app. '.apk's are basically like .exe installers which you can open from your phone's file browser. Note: opening random .apks is generally not a good idea at all security-wise so try not to download them from unknown sources (not that I can vouch for qooapp but it should be at least relatively alright)
Open this link for QooApp on your android device and download it. Once you have that you should be able to download T7S (as well as a bunch of other region-locked apps) from that app!
Last time I tried to help somebody with this, they were running into an error opening T7S once it was installed. This app is pretty commonly used for android users to play Japanese apps though, and I've never had a problem with it, so just let me know how it goes!