Can I delete backups from my "time machine" external hard drive?

I've had a 2tb "my passport" (using Time Machine) connected to my several year old Mac mini and the passport has been slowly filling up. I've got 200gb remaining. TM tells me it'll automatically start deleting old backups as necessary once the disk is full.

Question: are all those old, individual backups of any value? If I ever needed to restore the computer I'm pretty sure I'd use one of the most recent backups, not a 4 year old backup.

Question: can I manually delete my older backups that are taking up so much space on the backup device?