Oracle database Architecture
A. Oracle searches for a init.ora to determine the configuration
parameters

without a parameterfile, you will get an LRM-00109, ORA-01078 error, and nothing gets started

E. oracle starts an instance

we could argue what exactly starting an instance means, I have just simply put it here because this is the "exact" message that appears first when starting an instance

C. memory for the SGA gets allocated and the background processes that are necessairy get started

background processes like LGWR, DBWR, CKPT, SMON, PMON start in NOMOUNT, way before doing anything with control files...

F. oracle searches for the control files with the parameter CONTROL_FILES

thats the next one when going to MOUNT

D. Oracle searches the database files and redo log files

now tell me, how could the database perform an instance recovery without knowing where the datafiles and redo logs are

B. The proces SMON sometimes executes an instance-recovery

finally an instance recovery is performed, and database gets opened