Upgrading SEP 11 to SEP 12 - virus definitions ??

Does anyone know whether when upgrading SEP 11 to SEP 12.1 , and if the SEP 11 has up to date virus definitions, does the machine retain
the same virus definitions if you do an upgrade without full content or does it request a full update for SEP 12.1?

What would the typical update size of the virus definitions be if the machine had SEP 11 with a) 1 month old b) 2 month old , c) more than 3 months old

after upgrading to SEP 12 - how much would the client need to get up to date with all features.