Can it really? Can they dock together? The common dock is with the Space Station. So any rescue would have to happen before the StarLiner would leave the station.
No, they can't - but they should.
Both docking adapters are based in the International Docking System Standard, which allows docking ports to be androgynous (active or passive). However, what Boeing and SpaceX have built only have the active components, they don't have the passive petals for an active docking ring to grab onto for the soft capture.
In both cases, those parts could be added, but they haven't been so far.
Have you seen the new suits? They don't look like EVA suits at all , but what do I know.
Is the Dragon designed to open a hatch to raw space? We never saw an Apollo need to do it, but it was in the specs. Gemini was the two seat sports car that did. It's still the fastest 2 seat vehicle on record, Gordo Cooper's was a single seat record.
Docks likely be Male to Female, a rescue would need a docking adapter I would think.
Multiple spacewalks were done from Apollo capsules which required depressurizing the capsule, such as when repairing Skylab and during the later Apollo missions to retrieve film canisters from an experiment bay in the service module.
The Intravehicular Activity suits used in Crew Dragon and Starliner have no life support systems and are tied to the capsules life support with short tethers. They can only be used in their seats, in case of emergency depressurization. SpaceX has developed an EVA version of the same suit with a long tether, that will be tested later this year on the Polaris Dawn mission, along with the systems to allow Crew Dragon to repressurize after depressurizing. Due to the tether, those suits won't really work for transferring between vehicles.
Presumably, for a rescue mission, the rescue capsule would need to be equipped with passive capture petals. The reality is that neither Crew Dragon or Starliner can be prepped to fly an unplanned mission in the amount of time either vehicle can support a crew in orbit.