ditto_girl
Okay, I'm probally being realy geeky and thinking way to much about this but, hey! In the first movie when it goes from Lady sleeping as a pup on Jim Dear and Darling's bed. She then grows up and goes about her morning buisness. When she's at the breakfast table Jim Dear says 'Hey, she must be about sixth months old now. It's time she got a licence.' Now, correct me if I'm wrong but that implies that before she is that old it doesn't matter whether she has a collar or not when caught by the dogcatcher. In Lady and the Tramp 2 Scamp must be younger than that right. So does a licence only protect dogs from being destroyed.
As for Tramp's age, he's probably hella older than Lady. (after all he established quite the reputation for himself. No way that woulda happened in a matter of weeks). And quite a few MONTHS pass, probably around a year, before those two even meet up again.