Do all two bedroom units in the Maui Ocean Club have lock-off capability?

Yes all 2BDRM units that aren't part of a 3BDRM unit do lock-off.

What is the name of the original building that converted from a hotel to a timeshare?

Not all 2 bdrms have lockoff capability. They all have an interior privacy door that seperates them from the living room but not all have an exterior entry door that makes them a lock-off unit, some do.

Do you use the same key for the main entry and door to the lock-off room if you book a 2br suite in Molokai, Maui, Lanai towers?

Oceanview units in the Lahaina Towers do have some non-lock off 2BDRM units. All the 2BDRM units in the original towers are lock-offs. All 2BDRM units in Napili towers are lock-off units.

Does the old Lahaina Tower only have one bedroom?