If I animate Sword of Feast and Famine with Sydri, Galvanic Genius does the sword just become a vanilla 3/3 with an ability I can use or does it become a 5/5 with all the abilities of the sword?
Sword of Feast and Famine will become a 3/3 artifact creature (C.R. 202.3) and will still have its abilities — and will become unattached to anything it's currently attached to (C.R. 704.5p). (In general, when a permanent gains another card type or becomes an "artifact creature", it doesn't lose its abilities unless the effect specifically mentions otherwise [compare Sydri with Titania's Song; see also C.R. 205.1b and this thread].) Because Sword of Feast and Famine will still have its abilities, you can still activate its equip ability, even if that ability won't do anything when it resolves (see also this thread).
If I animate Sword of Feast and Famine with Sydri, Galvanic Genius does the sword just become a vanilla 3/3 with an ability I can use or does it become a 5/5 with all the abilities of the sword?