I dont know why Acronis didnt back them up. You will need to check how Acronis is backing up
As for getting the old ones back, no you cant. but at the same time you dont really want very old reg backups. You want to keep fresh ones and when something messes up you go back to the newest backup.
The reason why is after you do a lot of windows updates, changes to the system and so fourth and then restore a very old reg backup you can end up messing up the system.
It is best that before you do anything major do a reg backup, or the daily backups work great.
Shane