@svetlana Yes, sandboxing is quick testing. And yes, you have it right, If you keep regular backups of mongo in that setup, you'll be fine (along with saving copy of your config, to be complete).
If you want to really be good at deploying and upgrades, then at the bare minimum you should know how git works, how to change node versions, and how to set up / back up mongo. Everything else has pretty much been scripted out. Most of this stuff is either in the wiki or on this forum, you just have to look a little
Hacktoberfest is an annual celebration by Digital Ocean, GitHub, Intel, and DEV Community to promote participation in open source projects, such as NodeBB. All you need to do is submit 4 pull requests within in the month of October!