Can I swap a SIM card back and forth in an iPhone 5S?

Hiya, i'm clueless at anything related to phones and SIM cards.
Me and my sister currently share a iPhone 5S (until we can afford another phone), we both value our privacy therefore we want different phone numbers. If I bought a SIM card could we swap it in and out of the phone? Would it delete any data from one SIM card? And will a SIM card change the number? Also if the phone is on a contact Vodafone tariff would I need a SIM card from Vodafone?

Should I still buy the iPhone 5s?

I will be getting an iPhone in June. I have a certain budget that i can't go over. I don't think i can afford the iPhone 6s or the iPhone 6. I'm looking to buy the iPhone 5s. Is it still worth it to buy the 5s since it is an older model?

Can I get my AT&T iPhone 6 unlocked if I still owe on it?

Here s what happened. My mom and I had our plan with AT&T and she dropped it and switched to Verizon. Our contract isn't up until July and I work minimum wage and can't afford the $200 bill so I was going to switch to straight talk or Verizon but domt want to unlock it if it's illegal.

My tax refund status went from 'accepted' to?

For a week it has said 'accepted' today when I checked the status bar is gone and it says something like your return is still being processed, a refund date will be issues when available.

BUT when I check the status on my desk top computer it says they have record of my return?

What could this mean?

Added (1). Are there any tax experts that know why the status would differ from checking on my iPhone to checking on a desk top?