it is definitely a NAS, but I am sure that if you setup some port forwarding on the router, you could access it from outside the LAN. I however, would not recommend doing that.
Edit: It should support FTP just configure FTP on the NAS and setup portforwarding on your router…then use some dynamic dns program(so you can still get in if your IP changes)
Honestly, if this were me, I wouldn’t even bother with a NAS solution. Just setup sftp on computer on the network, forward the port and forget about it. Then you could just use ftp capabilities through your web browser or one of the many free ftp programs.