1) Does the new upgrade version require me to enter any serial number?
Yes
you need to go to
https://fileconnect.symantec.com for downloading (MR4 First and MR4 MP2 next)
select english it will ask for serial number
2) will the serial number of the old version 11.0.3001 MR3 work for the upgrade version 11.0.4202 MR4 MP2?
Yes
Your serial number would work for all your product catalog with Symantec, like mail security, backupexec.....etc
Have a good Day