FAQ - mrbrdo/mruby_cc GitHub Wiki
You can if you define MRBB_COMPAT_INTERPRETER in build/mrbcc_out.c. However it has not been tested extensively.
You can compile a .so with an extern mrbb_exec_entry_point, then you can load this module with load_compiled_mrb. For an example look at build/mrbcc_out.c.
Yes, just load the .so file and call its mrbb_exec_entry_point. For an example look at standalone_runner/mrbcc_runner.c.