Yet another smart key question

I am thinking of buying a used key from Ebay for my 2008 Prius that has the SKS fob (silver logo). After reading many posts here, I am still slightly confused.

1) Can the car be programed to accept a used silver logo fob? Would the procedure outlined in other posts for the black log fob work or must a dealer do this? I assume that the fob could only be use to start the car if it is placed in the slot and that all other functions would not work. From reading other posts, i believe that some people have been able to do this. True?

2) Would a black logo fob also work?

3) If either 1 or 2 would work, then can I use any key from a 2004-2009 car?

My goal is a cheap emergency key.

 

Thanks for clarifying this.

One other question. Can the car be programed so that the lock and unlock buttons work? Other posts suggest that these buttons can be made to work on non-SKS system but I was not sure if it woulsd also apply to SKS cars.