Some really dumb questions about smart phones - please help

[SilkStalkings]

What happens when you take your sim card out and use it in a new phone? Does the old one still have your data and apps on it? Can it be used as an ipod without a simcard in it? Could you pop your simcard back in it to update your music etc?
Had always promised my iPhone 3 to my 11yr old when it runs out this summer but now thinking of getting her something else sooner (Tesco Galaxy + free tablet deal). We also have an iPhone-dock/speaker set she could have if/when the iPhone charger gives up the ghost, is this a red herring? should I forget about that as a variable in my decisions?
Absolutely clueless so grateful for any advice. Thanks

Simcards don't usually have any contacts or data on them, unless you actively specify 'save to simcard' when adding new contacts (which people don't tend to). So your old phone will still have everything on it and anything you want on the new phone will need transferring over.

But, most phones won't allow you to boot them up without a sim card (so no simcard can't be used as an ipod) and most are also 'locked' to certain providers. Thankfully it's as simple as getting a new pay as you go simcard (for the right provider, usually £1 or £2), put it in the old and you can use the old phone again.

Thanks!