Not having received any answers from the community and being under a deadline, I contacted HPE Support, who were EXTREMELY helpful. I cannot say enough how terriffic they were. For the 2620 series switch, holding the clear button for 2 seconds clears all passwords and does not affect any thing else on the switch, nor does the switch require a power cycle or reset after this. Just push the button and you are all set. As for renaming the "Public" snmp community string, you cannot rename it. What you do is use the CLI interface and create a NEW snmp communit string, and then DELETE the old one. This way you still have snmp, but do not have the "Public" snmp community string for hackers to target. My problem was that I was googling for ways to CHANGE the name, which you can't. Be sure to then create new passwords for an operator user and a manager user, which you can do in the CLI interface or the Web interface.