|But one thing, will you please introduce a few cheapest boards based on what I mentioned in italic on the question #1 line of my first post above?|
You said "The model of the board was indeed recommended by an experienced guy", so I recommend you ask that "experienced guy" for some recommendations.
|but the thing which is a shade odd is that why are they all 8-bit?|
I pointed out those products because you said you wanted something cheap and easy. The products I pointed to (3 from several dozen from that manufacturer) are both cheap and IMO are very easy to learn.
|The first program in that book is about making an LED blink as well. |
Yes, so? Almost any micro-controller can "blink" an LED, but they will all probably need slightly different code to "blink". If you intend to follow that book religiously you really need to find out what processor/development system the author is using, otherwise you will need to reinterpret the code and wiring for your particular system.
By the way "embedded" systems are more involved than just "programming". You must know a little about electronics as well (the more the better) since you will need to wire components to your processor before you can actually program them.
Oh, and the author of that book hints that most, if not all, of the "projects" in the book can be handled by an 8 bit processor.
|My desire will most probably be the popular MCU called ARM Cortex-m, for instance, but now I have no idea about how to use C++ to program and deal with it.|
Again until you really decide what you want to do picking one particular processor is a bit premature (IMO). Decide on what you want to do before you limit yourself to one particular system.
One of the reasons I also suggested the Raspberry PI is that this board has a header file for some input/output pins and there is a lot of different projects that you can play with without needing to worry about cross-compiling code on one processor for another processor. You can use one of many different IDE natively on the PI making it much easier. Also there is a ton of excellent documentation for this board, and lots and lots of different projects available to try, from simply toggling a led to communicating to another system thru one of several different methods. The PI was designed with the "novice student" in mind and their primary focus is students. And by the way the PI is using an Arm Cortex Microprocessor.