When I bought my 520 from AT&T, they would not sell it to me without a $10 GoPhone account (I did not tell them it was for my regular AT&T account). I have heard that you can find some AT&T stores which will sell the phone without the GoPhone plan, but that seems to be the exception rather than the rule.
I turned off iMessage on my iPhone 4S, pulled the SIM out, put it in the 520 and it works perfectly. Voice, data, VVM, SMS, MMS, everything.
So, OP, given that you're talking about a 920 and a SIM I can only assume you're on AT&T. With that in mind, yes, if you get an AT&T 520 you will be able to freely put your 920's SIM in your 520 and it will work perfectly.