Multiboot: choose booting on wanted os before rebooting

I develop a project for my work. and at each big step I create backups of my entire sd. When the project will be launched I will continue to work on it and make my backups. but to update the pi on the ground I have to make an update system. I already thought of a web server with sftp. and the pi would come to query to see if there is a new version. if so, download the image. then I have to use the command dd bs = 1MB if = the image of = the main partition. however we can not do that on the score we use: p so I thought of the berryboot (heard on Google: p) but I never manipulated. my question is: is there a configuration file that manages the choice of boot, and can we modify it with nano to manage the next boot without having to plug the pi to a screen? cordially

I would like to know this as well