Instagram allows the public to make accounts for free.
I don't consider any web site or service that requires a phone number to be provided in order to create an account to be "free", both in terms of cost and liberty.
No, you can sign up with just an email address assuming you don't look like a bot.
As far as I'm considered, Instagram absolutely needs a phone number. Officially they don't need one at sign up - but they won't allow you to use that account for long before you need a phone number anyway.
Sure, but this is a 1 time cost and most people already have an account. I'm sure it also takes several minutes to set up your internet or phone too.
>and never got the phone number confirmation code
Are you potentially using a phone number from a service like twilio instead of your actual phone number? VoIP and related numbers are usually banned because they are mostly used by malicious users.
Keeping track of the posts you've like is a feature of the app. Personalization is also another feature of the app. Tracking the time you have the app open is why you can see your screen time and how you can set screen time limits. These are features which users find value.
If you don't want this data to last a century you can just delete your account and your data will be deleted too.