If I click this, I know it's random. But with biting, can I be bit by someone with a specific strain and get that strain? Or will it still be random?
Yeah, it depends on who bites you. If you choose that option and someone bites you with the Love Bug virus, then you'll get infected with Love Bug. If they bite you with something else, you'll get that thing.
So it's nice because it's free, if the virus you want is one of the more expensive ones. But it's slightly riskier because someone else could bite you with a virus you don't want. Although most people I think are considerate and don't bite people unless asked.