No. Even if you applied to a new job that related to all this it would generally be understood that as a new grad you're not going to know this stuff, and either A: the job would never have been posted in such a way as to lead you to apply or B: they understand there's going to be on-the-job training.
That said, if you're specifically applying to CloudFlare, you just got handed a great study sheet to differentiate yourself very handily from your peers. You'd think that "everyone" looks for this sort of thing, but given the ongoing streams of reports of "people who fail FizzBuzz", no, seriously, few people look at this sort of thing before interviews!
Only if you plan on becoming a low-level TCP/IP implementation engineer or some other such niche field in the very immediate future.
The vast majority of working programmers can be extremely effective without knowing much more than basic socket usage and perhaps the basics of how NAT setups can work against you if you're doing something other than just pure web-browser networking.
Having said that, knowing how in-the-wild network protocols work in general is one of those things (like knowing how compilers work) that can broaden your horizons and are probably worth learning for that reason, just don't worry too much about retaining minutia about them that you can easily look up should the need arise.
No. And if you run into a company where they do ask these questions (and others like them) and take them seriously, then try really hard not to work there because it will probably suck.
Why should you? These are tricky domain specific questions that a network engineer with intimate knowledge of TCP/IP could answer some of. I certainly wouldn't expect a fresh CS graduate to know these things unless you did a lot of work in that area for some reason.
No. If you can't figure them out from reading the relevant RFCs, then maybe (reading specs is a vital skill), but this is absolutely not stuff that's worth memorizing (at least for most CS jobs).
