How to upgrade manually built packages in linux?

Question

linux

I'm just starting to learn Linux and I have the following question:
apt-get has a list of repositories, installing packages from which I can update them in the future by update && upgrade.
1. If I manually add a repository and then install a package from it, can I also just update it later via update && upgrade?
2. If I compile a package manually from sorts, then, as I understand it, in order to update such a package in the future, it will need to be manually rebuilt?
Do I understand correctly that:
1. The repositories contain ready-made assemblies with default configs for different platforms and apt-get simply selects the one you need during installation.
2. If you don’t want to manually rebuild the package each time to update it, you need to have an added repository where the good guys have already compiled the latest version of this package for me.
Thank you.

Answer 1

1. Yes, that's what packages and their managers are for.
2. Yes, that's right.
1. You, in principle, choose what to put.
2. Again, right, but you can download the package from the source code and install it via dpkg -i