HOW DO I UPDATE MY IPAD 2 TO IOS 6?

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What's the relation between iOS and memory? iOS is operation system which is not lessen your memory. So, if you can't download twitter, it doesn't related with the operation system. Your problem is that you have loads of programs and you have no memory enough to download ahead. So, delete some apps which is not being used by you, especially games, because they take a lot of games. I don't write games which you have purchased, just unusual. When you clean up to 3 gb, then try to download twitter. And be sure that your operation system is iOS 7, because the new twitter with new design works only with iOS 7, I reckon.