Yes, MANY.
Not in our solar system. Nor have any been found elsewhere to date.
YeS, numerous solar systems actually.
No alien life has been found so far; either inside or outside our Solar System.
It is so large that it has never been lost.
Planets found outside our own solar system are called exo-solar planets or exoplanets. These are in orbit around other stars. It's ver difficult to detect them due to the distances involved, but with modern techniques, over 500 have been confirmed.
Jupiter is the biggest planet in the solar system. However there have been 'super Jupiters' found orbiting other stars.
The Sun
It has been suggested that comets originate in the Oort cloud and then travel in long elliptical orbits around the Sun.
The age of the Solar System HAS TO BE at least as much as that of the oldest rocks found on Earth, other planets, or asteroids (if you assume that those rocks come from the Solar System) - and that's what has been found. And that's the approximate age of the oldest rocks found. The main methods used rely on radiometric dating. For more information, check the Wikipedia (or other sources) for:* Age of the Earth* Radiometric dating
Yes, the planet Earth is part of the solar system, so all the life on Earth is in the solar system. Yes, our Earth is part of the Solar System. As to life on other planets - both within our Solar System and in other solar systems (planets around other stars), nothing has been proven yet, one way or the other. Specifically, no life has been found on other planets. It would seem probable, though, that what happened on Earth can happen again - perhaps on nearly any planet, perhaps only occasionally.
Jupiter is the largest planet in our solar system, but not the largest planet of all. Planets larger than Jupiter have been found orbiting other stars.
The meaning of the term "alien world" is somewhat ambiguous. No evidence of life on any planet in the solar system except earth, or on any planet around any other star, has yet been found.