Repaying for already purchased games

How did you buy them ? All of your apps, whether free or paid-for to download, will show in the Purchased link for redownloading (as long as you don't change countries and the developer doesn't remove them from the store, and you are logged in with the same account).

If you made in-app purchases within an app to update them then whether you can redownload the IAP depends upon what type of IAP that it was : iTunes Store: About In-App Purchases. If they are IAPs then have you tried logging out (tap on your id in Settings > iTunes & App Store) on your device, done a soft-reset of it (press and hold both the sleep and home buttons for about 10 to 15 seconds, ignoring the red slider, after which the Apple logo should appear), and then logged back into your account to see if you can then redownload the IAP ?

You need to be signed into the account in Settings > iTunes & App Store that you bought/downloaded the apps with - the apps that you can redownload for that account will then show in the Purchased tab in the App Store app with a cloud icon against them (if they are already downloaded then they will have 'open' against them, not the cloud icon). If you are redownloading on your computer's iTunes then you need to be signed in via the Store drop-down menu, and you can then redownload via the Purchased link under Quick Links on the right-hand side of the iTunes store home page.

If they are in-app purchases that you made within the game to upgrade them then you might be able to redownload those IAPs within the game - but whether you can redownload them depends upon whether you are logged into the same account that you originally made the IAP with, and what type of IAP it is. If you are having problems redownloading an IAP then try logging out and back into your on your device and then re-try