While you are on the site, in your browser find and click "Add to Home Screen" A CGN beaver app icon will then be created to your phone that is directly link to the site.
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I'm sure there's no obligation to destroy the old card. Always be sure that you're carrying the correct card,though. Don't get them mixed up. That could be a tad embarrassing.
I keep my previous one just in case I lose the new one. The only difference is the number after the . and possibly the expiry date.
When I do destroy mine it is like any other card. It winds up in teeny pieces.