This may be of some help (do not literally write out the backslashes '\' in the commands, they are meant to indicate that "everything has to be on one line"):
It seems that all the commands (in grey) take any type of key file (in green) as "in" argument. Which is nice.
Here are the commands again for easier copy-pasting:
openssl rsa -in $FF -out $TF
openssl rsa -aes256 -in $FF -out $TF
openssl pkcs8 -topk8 -nocrypt -in $FF -out $TF
openssl pkcs8 -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA256 -in $FF -out $TF
and
openssl rsa -check -in $FF
openssl rsa -text -in $FF