Selfhosted

Kubernetes has a hell of a learning curve. Once you get your head around it, it can be great but it is a huge lift to learn. For self hosting I'd lean towards docker-compose rather than kubernetes but kubernetes can be nice once you get past the super steep learning curve.

To answer your questions:

1. Any Linux flavor will do the job.
2. No, windows doesn't really play nice with containers to begin with. Kubernetes is another layer of complexity that will make it tough.
3. Yep, definitely! This is typically done using helm charts. Helm is basically the package manager for kubernetes. There are many helm charts that you can just install into kubernetes and they'll work for you. You can also roll your own if you have custom applications. Argocd can also be helpful depending on how deep you want to get.
4. I'd start by looking into videos on helm charts. That said, you will need a very strong understanding of docker containers and may need a good understanding of networking.

I would strongly recommend looking into deployment using docker-compose over kubernetes until you understand containers inside and out. While Kubernetes can be nice it akso adds another layer of difficulty. I say this as someone who uses kubernetes daily for work, uses off the shelf helm charts, and writes their own helm charts from scratch.