Yes it is, It is 100% compatible with the Spectra plugin
Spectra One tries to be minimal but at the same time brings useful features to its users. other fse themes just provide patterns and nothing else
Spectra One is a block-based FSE theme. This essentially means that it’s the new way of designing WordPress websites. Everything is customized in the new WordPress site editor rather than the customizer. The entire website is built visually using the block editor.
Yes spectra one is 100% free forever
Astra and spectra one are two different themes and not evolution so when you move from Astra to spectra one it will behave the same way as any other theme.
We are currently working on the same
Yes it’s possible to add more, for now, you can add fonts ( google fonts ) using the spectra plugin. Refer to this document for more details.
It is possible that this issue arises due to the presence of unremoved customizations. Please be aware that clearing the customizations will undo any changes made by the user and restore the layout to its default settings.