Firstly, you should be searching for this information. You've been here more than long enough to know every single question you could possibly ask has already been asked/answered many times. As this phone was released 3 yrs ago, this is absolutely the case.
Having said that, I will supply you brief/limited answers to your questions (I am not providing detailed answers for the above reason; I'm not doing your work for you).
1) Don't use CFRoot. It's been superceded. Search for the PhilZ thread & use that (do not ask me 'what kernel do I use ?'; read the thread).
2) You should be able to use any version of Odin, however, if you find one version doesn't work, try another. Also, if you have problems with any Odin flash, refer to Hopper8's 'Odin troubleshooting' thread stickied in General.
3) Not applicable due to the answer I gave in 1.
4) No, you cannot flash another version of CWM independently of anything else like you can on other phones. Recovery is 'baked' into the kernel on the I9100 & not in a separate partition like other phones, so any recovery you flash independently will only persist until the next reboot. You're stuck with whatever CWM version the kernel uses.
If you want a particular CWM version, you need to run a kernel that has it (read the kernel thread to find out which version it uses).
5) This information (which CWM version at a minimum you need to flash these roms) is absolutely common knowledge now & has been asked/answered 100's of times at least over the past few mths since these roms were released; search.
Edit - Whether it's your phone or not is irrelevant. If you're going to mod this person's phone for them, everything I've said holds true. If they're going to do it themselves, they would be much better served by taking the time to actually learn this stuff themselves. I'm tipping a busted phone & a lot of tears if you pass on the information I've given you.