Do I need to install it on my phone or the one that I want to monitor?
This application did require to be installed on the target device (the one you wanted to monitor). However, this application is discontinued so you can't use it anymore.
Yes, of course. Software like Mobile Spy should be installed on the target cell phone you need to monitor. You will view logs remotely on your control panel.
Yes, but one thing to remember, if you install such kind of spy app like iKeyMonitor without any permission, you may break the law and be accused.