1] yes, but this sound pretty logical right? one license, one pc. but ofc. if you buy a new pc, or your pc breaks down etc. you can transfer the license to another computer. no problem. i just moved w8 from my old pc to my new one, need to call MS where i got an automated tape and had to punch in some numbers. was done in 5minutes.
2] shouldn't be a problem, you can transfer windows from hdd to sdd, since its the same computer it shouldn't be a problem at all. search the internet for best practices to move to ssd, probably using some free cloning software or maybe even using the build-in options of w8.
3] OEM is only for newly sold computers, its not allowed to install OEM on old computers. other then that is exactly the same, with the exception that you can't upgrade w7 with it (as its not meant for old computers). support is the same.
4] see question 3
5] learn to google.