Greetings all.
Thank you in advance for providing input to my search. This would be very helpful in my research for a project.

A long time ago I read that the US. Gemini manned spacecraft used an inertial guidance system that had 4-axis gimbals. Presumably this was to help prevent gimbal lock. Is this true?

I have been seeing a lot of historical information (on internet, film, TV, etc.) that suggest the US manned Apollo program used 3-axis gimbal system, thus all the references to potential gimbal lock. Perhaps even a reference to that in the movie Apollo 13.

Is it true that earlier Gemini flights had 4-axis but the Apollo was built with 3-axis, presumably to reduce weight, size, cost, and complexity?

Regards.
Gary