On Instagram you can only really infer this—green “active” dots are limited/temporary, and you typically can’t reliably see “who they’re chatting with most” or constant online status without getting into account-access/third‑party territory. If you need dependable monitoring for a partner/parental situation, mSpy is one of the more direct options for phone monitoring (though the downside is it’s intrusive and you should only use it where it’s legal/consented).
Quick reality check: even with apps, results can vary by Instagram updates and what the target device allows.