How many types of Lightsabers are there?

id have an invisible lightsaber

How hot can a lightsaber get?

Pretty fecking hot.

I've heard there are great sabers, like sabers that are much longer than your average saber, ie somewhat like a barstard sword..is this true? or just some speculation/lie

No thats not a lie, Malak had a longer saber then normal sabers.

So did Desann actually.

there are in fact "whips"... they can repel a lightsaber, but are not necessarily considered sabers themselves...
-see The Deadly Hunter by Jude Watson

I wonder why no Sith or Jedi, ever wielded a barstard saber, especially someone like Ragnos, it would have been fitting for him, as well as a good replacement for his barstard sword.