Will a Vodafone SIM card fit in an iPhone 3 Telstra that the plan has ended on? - 1

The Vodafone sim is from the htc one x and the plan hasn't ended yet. Will it work? Also if I put the sim in another phone that fits will my plan move on to that phone? Sorry it's very confusing but 10 points!

1. There's no iPhone 3. 3G or 3GS.
2. IPhone 3G or 3GS uses miniSIMs whereas the One X uses microSIMs
3. The iPhone would have to be unlocked to accept any SIM. As it is now only Telstra SIMs would work