The gravitational force of the sun on other planets including Earth is not unoform throughout its area. It is maximum at the centre of the Sun. This makes the planets come nearest to the Sun at its centre and farthest from it at the poles of the Sun. Due to this, the path that these planets follow while revolving around the Sun is slliptical.

Another inportant thing in the second part of the question is that, there is only one Sun, planets do not have their own Suns, rather they have rheir own Moons. So all planets revolve in elliptical orbits around this Sun.