Apple provides a lot of choices through “Family Sharing” where parents manage settings through iCloud. You can restrict apps, times, duration, content by ratings, websites, purchases, calling, etc

When my kids were little and got their first phones, Family Sharing didn’t really exist yet, but there were apps that might be more similar to what you’re thinking. However my restrictions actions were pretty minimal - mainly to limit screen time overall and after lights out

• my kids were especially annoyed about blocking mature content on YouTube - most videos are unrated so the all get blocked. It’s just not worth trying
• when I tried blocking explicit web sites, they just used other devices. While I expected them to find a way around the restrictions pretty easily, it was ridiculous how many different types of devices Id need to do that on, and each did it a different way with different capabilities. It’s just not worth it. Pay attention to your kids and trust them instead