First time Android user myself, been reading for the last week and I've learned quite a bit though. All info can be found in XDA forums if you use search feature.
1- How can i find my phones Model ID / MID or CID / Cidnum ID ??
download Android SDK (adb/fastboot) and with the device connected in fastboot mode, type fastboot getvar all. It will tell you the versions of everything.
2- How can i identify what set or version of ROM package is compatible for my HTC-ONE ???
All ROM's say which device they are compatible with. I think all except for Sprint (in USA) are the same. The best way would be to use the HTC ONE _carrier_ forum and click on Android Development under there
3- Whats this RADIO ?
RADIO is the Antennae firmware used by your device for wifi/bluetooth/signal
4- Whats S-On and S-Off... [Just read its Security on and off]. But should i need it ?
Dont worry about this, this is one step further than ROOT. It grants you access to even more things like changing your CID/Model number so you get OTA updates designed for another carrier.
5- Whats this Odexed and De-Odexed ? And what my HTC-ONE has currently as stock ROM odexed or de-odexed ?
I forgot exactly what it was, I found the explanation in google.com basically deodexed lets you install some things odexed does not use google for this.
6-Will i get an .exe JB update for my HTC-ONE after identifying what version of ROMs i need ?
7-Where can i download the Revolution HD ROM ???
There are two versions, one based on Sense 5 and one on Google Edition:
step by step instructions can be found there, that is how I learned myself.
7-Finally , How can i flash any ROM to my HTC-ONE... with out hassle... [tried with HTC Tool Kits Update RUU option, but shows error cant load "xxxxx"
follow the steps posted on the ROM thread of your choice. I've read some ROMs require two steps (one flash ROM one flash boot image) but ARHD 12.2 does not, it is easy to install. There is a video in youtube that shows some guy installing ARHD 12.0 which is the same process.