I allowed my son to download an app from the store, but now I know it is one I do not want him to have. Because I allowed it once and entered the password he is able to download whenever he wants without a password. Any way to make even those apps require a password?
iPhone 6
No. Sorry.
Try 'Settings app > iTunes & App store', tap your Apple ID & sign out.
The list of purchases should be unavailable until you sign back in to the store.
Also see 'Settings app > General > Restrictions' there should be a setting for the password timeout (mine is under 'Allowed Content'). Set that to immediately to see if it helps.
I'm looking at iOS 7 so the settings may be different for you.
I also wonder if you can use the hide purchase feature within the iTunes store, but I don't know if that will help, sorry, navigate to your purchase history & try hiding them.
Hide and unhide purchases in the iTunes Store - Apple Support
How do I require a password for previously downloaded apps?
