You cannot use a certificate for more than one LH flight, nor for a UA flight followed by an LH flight (unless you get an incredibly nice UA agent I suppose). You can use a SWU for multiple UA flights in one direction.

LH will add you to the list when you reach the airport where the segment departs, not from other airports. I don't think it matters much anyway because upgrading is primarily goverend by your status including *A status. If the flight is wide open for upgrades, they will often confirm it as soon as you request it (unlike UA where you essentially always wait till the gate)

Charles