Is the uppercase implementation of Android the only thing that is trademark, like it is with Google or both, because android is in reference to a robot?
If they did trademark both does that prevent the use of android, in reference to a robot, in any works of fiction without prior approval?
Trademarked words are filed in all capital letters so an upper or lower case "a" does not make a difference. More generally, any variations of a mark that would be confused with the original would be trademark infringement so adding/changing a letter or two or punctuation is probably not enough of a difference in most cases.
Alain's answer is correct, but you need to watch out for other trademarks as well. For example, Lucasfilms has a trademark on "Droid". You may not infringe the Android mark, but you may infringe the Droid mark.
Note that Motorola licensed the Droid trademark from Lucasfilms for its Droid phones. Here is an article about it.
No. Trademarks apply for a specific domain only. If you talk about a smartphone platform, you can't use the word Android if you are confusing people. But for robots, it's probably clear (I haven't checked the actual trademark to see which domains are covered). And trademarks don't mean you can't use the word, but you have to respect its meaning.
The word "android " to describe a robot was coined a long time ago and is now in the public domain, so anybody can use it to describe robots.
By the way, "droid" is a separate trademark from "android". Motorola has the trademark for "droid" but they pay a licensing fee to LucasFilm, who holds the copyright.