about 403.
yes, there are many things outside the kuiper belt that we have discovered. all of the stars you see at night are outside of the kuiper belt. we have discovered galexies, exoplanets, and many other things.
As we are discovering more and more exoplanets almost weekly, there will never be a "last" planet discovered.
There have been 95 exoplanets discovered in 2010. You'll need to be more specific on the question.
I believe some of them can, but mostly, the exoplanets are discovered and observed with more indirect methods - especially by analyzing the gravitational effects on the star.
See related link for a full list of the all "known" exoplanets
A few thousand exoplanets have been discovered so far; according to the Wikipedia article on "Exoplanet": "As of 1 March 2017, a total of 3,586 confirmed exoplanets are listed in the Extrasolar Planets Encyclopaedia".The Wikipedia article "List of exoplanets" has a list of such exoplanets.
Once upon a time, the answer would have been a confident, "Jupiter," but recently almost a thousand "exoplanets" have been discovered, many of which are bigger. From what we know of planet formation, we THINK these are gas giants, planets with vast atmospheres and small, rocky nucleii.
Now we know of 861 exoplanets, with several thousand awaiting confirmation
Most exoplanets so far discovered resemble Jupiter. However, Earth sized planets have also been discovered and more will be discovered.
There are many exoplanets that have been discovered during the last 12 years. See the sources and related links below for Wikipedia's article on exoplanetary systems. Most were found this millennium.
none of them
water was recently discovered on planet mars