I’d need more details about how it works, like can I get onto their iPhone via the Internet or the cell phone network no matter where or who they are? Are my senses then limited to using the iPhone cameras and microphone? How long does the transition into and out of the phone take? If I’m in someone’s phone, can I opt to return to my own computer’s location instead? If they drop their phone and break it, do I die? Can I take any objects into and out of the phone or my home device, so I can use it to steal, or bring equipment with me, or do I appear nude like the Terminator?

If I can target anyone this way, I’d use it for intelligence gathering on bad actors such as GQP politicians, foreign heads of state and military, evil CEOs, etc., to get incriminating information and other vulnerabilities. I’d probably try to make due with the camera and microphone access in order to avoid detection and vulnerability.

I would delete their selfies.
Just the selfies.
Whenever they snap one: delete it.

Doing voyeuristic stuff will be very tempting but eventually I might offer my spying services to people who have plans to sabotage the nuclear weapons capability of people I deem to be evil. Lol

I would cause the phone to exploded due to a battery problem.

You mean like Ant Man? Not sure… BUT
I would love to motorize myself Oh Yeah!

This sounds very much like NSO group’s Pegasus software .
No need to shrink yourself. Pegasus will email you.