Pro-tip: these "services" are all rubbish. If you could circumvent their privacy controls that easily, it would be a pretty significant issue for IG and Meta. The way to view private IG posts is to connect with the account or have the login credentials to the account. Anyone telling you there's a secret back door is shoveling horseshit. (A secret back door that random internet users can access, anyway.)
So if these methods work and aren't scams, why are you asking about them? If they work then you have what you need? It might be worth keeping in mind that if a girl has their profile on private it's because they don't want people like you looking at their personal shit. Your time might be better spent trying to find a woman in the real world who actually wants you to look at her.
Isn't possible to view private instagram accounts, you'll need to add them as a friend to view their content. 100% of blog post's & website's you'll find on this topic, are SCAMS....