The only "unlimited" thing you'll get from that mod is unlimited headaches, malware scans, and regret.
If you cannot afford coins, find another app. If you are bored, close the app. But inviting a hacked executable into your Android device for a fleeting, fake sense of wealth is like burning your house down for a warm glow.
Stay safe. Pay for the service you use, or use a free service. There is no cheat code for human connection.
But irony is cruel: If everyone had unlimited coins, the coins would become worthless. The "premium" attention you buy would lose its value instantly. The scarcity is the feature, not the bug. Do not download the Pink Chat Mod APK.