How to delete google play? I want to disable or delete google play store (I don't want the person who has access to the device to install any apps, and I want to free up some space while I'm at it).

I have root. Where are the files stored (such as the apk, odex)?

Is it in /system/app?
Use titanium backup, which lets you disable/remove apps like that. Or, flash a new rom that doesn't include gapps, download a gapps package and remove the Play Store, then flash that modified package.