forgotten device password

I have had my macbook air for a couple of years. In the summer I turned the password off (I had it set so you had to plug the password in every time you opened the mac but we had house-guests who needed to borrow my laptop so rather than telling them my complicated password, I just turned it off). I then forgot to turn it on again and now it has been a few months and the password I thought was correct is not working as the device password. Neither is my appleID. I am scared to power off my computer in case I need to put the password in to get it running again so I have not been able to do any software updates. I have an external hard drive and have done a Timecapsule backup of the laptop. Is there some way for me to restart the laptop and then restore from the backup without knowing the device password?