Best practice for backing up a site collection prior to programmatic changes?

[Nissan Dookeran]

I have a customer with an existing Office 365 tenant and live Intranet production site in a site collection, and I wish to run some custom deployment scripts on this site collection to create new subsites, content types, and deploy a few custom webparts. I am not sure if there would be any conflicts with existing content.

I'd like to be able to back up the entire site collection and restore it to some sort of staging environment in my own Office 365 Developer tenant so I can test my scripts first to ensure no unexpected side effects occur that may affect their production environment, but I'm not seeing that option in Powershell for SPOnline, I'm guessing a third party tool is needed here? (If so, what tool?)

What would be the recommended best practice for ensuring a proper backup of this site was done, so that if something failed, a "point in time" restoration can be done that would restore the site collection to its original state?

Much thanks to anyone who can offer a guiding light for a path forward here that may not lead to any complications.

Regards,

Nissan

[#2]

Third party migration tools for SPO are quite well known and specifically two of them: Sharegate and Metalogix....any of both are good for what you need to do...in regards of backups I would go for two approaches:
(1) Make a copy of the site collection before starting the deployment using the migration tool you have finally chosen
(2) Invest also in a backup tool bearing in mind that backups need some time to be done. Here you have Metalogix and Barracuda Backup as my personal recommendations