How in the heck are credsticks suppose to work?, Looking for detailed examples Options

[deagol3]

I've been looking at the rules for credsticks, and I'm still not clear how they're suppose to work in the practical sense. For instance if a character has a credstick with a 5000 nuyen limit does that mean:
1. That it cannot accept any nuyen that would bring the total above 5,000?
2. That it cannot be used to purchase/transfer more than 5,000 nuyen, even if the character's bank account has more than 5,000 nuyen in it? If this is a limit does it mean that once the 5,000 nuyen have been spent the character has to go back to a bank?
3. For SIN verification I've seen it mentioned that street cops typically have a mid-level verification reader. What would the cops do if they encountered a character that had a credstick that used only the highest level of security (cellular scan)?

Am I getting second and third edition confused? Can anyone provide a "Dick and Jane" example of how credstick transactions would work?

Thanks in Advance!