On a stock (non-jailbroken) iPhone there’s no way for Maxxspy—or any 3rd-party “invisible” app—to get the deep system hooks it needs. If you do jailbreak, tweaks always show up in Cydia or via jailbreak-detection tools, so it’s not truly undetectable.
Instead, consider Apple’s built-in Screen Time with Family Sharing (totally transparent and tamper-resistant), or an MDM profile if you need more granular control. iOS’s sandbox and privacy architecture make it far more reliable and secure than the wild west of Android app sideloading.