In my opinion, yes. There are at least 10,000 trillion sentient species (100,000 per galaxy) in the observable universe.
Yes. There are at least 12,600 trillion intelligent civilizations (i.e. sentient species) in the observable universe (126,000 per galaxy). They come in all shapes, sizes, colors, unusual features, etc. There is also at least 100 billion in-universe reference books of them (excluding non-sentient ones), because in addition to their large portraits, they get a 1 1/2 page detailed description of their species, their histories and what planet and/or moon they're from, which is at least 189,000 pages in length per book. But for now, it is unknown.
To make 100 billion separate books of all of the information of 10,000 trillion sentient species (100,000 per galaxy) in our universe, you would need to begin by researching each species. Then combine the information using a computer.
Yes. It might be possible that there are countless sentient species in the universe, but we do not know for now.
You can make 100 billion separate books that has the descriptions of about 10,000 trillion sentient species (100,000 per book) by simply orderly compiling them.
Despite much debate among people and scientist, there is no official proof that there are countless semi-sentient species in the universe.
Though some scientist say there is a possibility that there are countless non-sentient species in the universe, there is no concrete proof right now to be sure.
Fiction authors have a free hand for what is in their books. However it is not known how many sentient species there are so the author may decide that also.
Not even a single alien race has been found so far. However, assuming for the sake of argument that there are, indeed, 10,000 trillion sentient species (100,000 per book), you would first have to gather all the information (where from?), then store it in some computer system. Both seem impossible tasks, at least for the time being.
It isn't currently known whether there is even a single species outside Earth - sentient or otherwise. The number you mention has been made up by somebody.
Currently it is not known. Earth is the only known planet to hold life so far. It also depends at what point you consider a living thing to be sentient.
For a start, it isn't known whether there is even a single sentient species in the Universe - outside of planet Earth, that is. There might be, but this has not been confirmed. Second, if there are, there is currently no way to know how many there are, or to gather information about them. Finally, even assuming you can get all the information, you'll have trouble storing that much information on even the largest computer system available today.
No. Sentience is not one dimensional but five: cognitive, recognitive, sensory, inherent, and logical. Each of these has a range value therefore the measure of sentience is n5 variable value.