Yes, with a dual channel Hive they should be a straight swap. The backplates are in theory supposed to be a universal fit, and generally they are, but I have found one or two to be a bit tight / loose though, across the various manufacturers.
However, I always swap the old backplate for the new one that came with the Hive anyway, then both parts are new together, and I know that the contacts / pins will align properly just in case there was any wear, or damage to the existing backplate.
Electrically speaking the two devices are identical internally, so if there isn't a wire in terminal 2 now, it won't be needed with the Hive either.
Apart from the N & L, S-Plan systems require a wire to 3 & 4 Hot water and central heating on
Y-Plans also require a wire to 3 & 4 Hot water and central heating on, plus a wire to 1, hot water off.
It's years since I saw a system use the central heating off connection (terminal 2). It was a system with a Momo (Motor on, motor off) motorised valve which requires a live supply to close the valve, as well as open it. Don't expect to see one though, they are pretty much as rare as hens teeth.
