A:AnswerI traded my 6s for the SE and got their promotional amount at that time. I went into the store and surrendered my phone, got a best buy gift for the trade in value so it will depend on their current promotional. You'll just have to watch for it.
A:AnswerIt should work fine, depends on your carrier plan but the phone supports GSM networks which Vodafone is, according to this UK contracting; https://www.vodafone.co.uk/modals/simo-more-details-rvb-12months/ there aren’t roaming charges and the phone should piggyback off of other GSM networks in the US.
A:Answerhttps://support.apple.com/en-us/HT209044
In short, yes. As long as your iPhone is carrier unlocked, you can have a second number/account through a carrier who supports eSIM (I believe the major US carriers do). On the iPhone if you only have one carrier account you can have your service through the eSIM only (no physical SIM required) but you'll have to take more steps if you need to change phones.
