Instagram stalkers are very sharp-minded, and they never reveal their stalking strategies. But If a stalker is your friend, then you can ask the strategies to stalk someone. I think he will tell you how he stalks someone and views the profile of others.
I can share my experience with you. Once I ask my friend to tell me some strategies because I have to stalk by a crush. He then shares with me how to stalk someone on Instagram; I can also share m knowledge with you. Just give it a quick read to the provided information below:

Ways To View Someone's Instagram
Here are some easy ways to stalk someone on Insta without their knowledge.

Finsta

Finsta is a second Insta account of someone, and that is fake. You can also create a fake account to stalk someone on Insta to protect your identity. Instagram is not much active in revealing someone's identity.
That means you can visit someone's profile and view their posts and stories without getting caught. Even third-party apps cannot fetch that data about a person's profile who frequently visits to stalk someone. Only in a business account, Insta insights reveal the visitor's count but not their identity.
Also, Read: how to see your Instagram stalkers?