How do you fly the TARDIS?
You will need to have a save where you already own the flight upgrade and boosters.
From there you can activate the mod, and the controls are the same as the delorean/mach 2

How do you change the reactor/fuel?
You can open the roof hatch to allow access to the reactor and fuel cells

Does this prevent time agents spawning in earlier centuries?
Unfortunately, no, since this is just a model replacement and not game changing code.

Will the TARDIS have sounds from the show?
Sounds are planned to be added properly in the interior update, however, there are some base sounds currently overwritten, made by 𝐓𝐡𝐞 𝟐𝟒𝐭𝐡_𝐃𝐨𝐜𝐭𝐨𝐫-𝟏𝟗𝟐𝟐