You are paid to build sht, not to answer questions.

- Eli the Computer Guy

So I just started watching Eli The Computer Guy's videos on networking and I really like them so far(only on the introduction so far though), but I was a bit confused about some of the stuff and I thought to myself that some of this might be obsolote or not so much in use these days/different. So here are some questions(now bear with me, I'm still a noob to the whole topic of networking):

-Are Eli's videos on networking obsolete(besides the speeds that he talks about), what you recommend some other tutorial, if so which one?

-Is a switch necessary for a small network?

-Do we still connect routers to modems or do we just use what we refer to as a router(a mix between a router and a modem -> gateway/gateway router)?

-Can you connect an ethernet cable to your router/gateway?

-So according to Eli if you have multiple routers they make seperate networks that cant just be acessed from each other, then how come it be that I can access my rasperry pi when I'm connected on the network of one router when the raspberry pi is connected to the network of another router and how come it be that once you have the wifi password you can connect to all of them?

So...about companies having way to big expectations on their job ads descriptions: Me being the new guy in all of this, of course I'm looking for more informations on the field everywhere. One day I came across a video on youtube posted by Eli the Computer Guy, and he was describing (caricaturing) this exact problem. You should look it up.
I'm not sure if he himself is a valuable source/resource of knowledge, but it did help me to understand this problem to some extent.

Hope it helps you too.