My friend has been playing for the last week and sent me a link to download it myself.

The "Referral Program" tab in-game states that we would both receive rewards when the game was installed from the link, but neither of us have received anything despite my having completed the tutorial.

He's running the game on an android phone and I'm on PC.

Hello, PM me your in game id and a link to this post. I will see what i can do.