What are the programs for synchronizing files?

Question

Data synchronization

You need a program to synchronize files over a local network.
Now I use Googledisk for this, but after increasing the number of machines to more than 50-60, it began to catch bugs, and even crash the account, which required me to go to the remote computer and log in again or completely restart.
I'm looking for an alternative without the need for authorization within the local network. (You can also with, if without bugs)
You can pay, if the money is reasonable.

It is also possible that knowledgeable people will tell me a version control program.
I don’t know exactly what it does, but I would like to create copies of files in some folder, without having to do it manually.

One more question.
I work in Python, I write in PyCharm, is it possible to mark a part of the code? For further quickly finding or deleting, if necessary, add temporary functionality.
Or delete the code written between certain comments.
The question is more likely to people who use similar IDEs, believing that if there are such settings in one, then they will most likely be in the other.

Answer 1

1. Owncloud/Nextcloud
2. Git

Answer 2

resilio sync (once known as btsync) - paid (there is a limit on the number of folders in free)
syncthing - a free open source analogue of the previous one.
p2p system, i.e. no explicit server. encrypted channel. demon, i.e. constantly monitors files and submits changes. there is versioning of the changed.