Can I repurchase a returned app?

Hi I just recently returned two iPad apps which I had purchased on the App Store, as those apps were not working too well on my old iPad. The refund mostly looks like it will come through.

Just two questions though.

1. What happens now? Will the apps simply stop working. And if so, at what point. Or is the onus on me to delete the apps. Never done this before so I am very curious as to how it works.

2. Will I be able to re-purchase the same apps at a later date if and when I upgrade my iPad to one that will support these apps better. Is it permitted and will they charge me extra in some way.

Thanks in advance for any replies.