Do blackholes exist?? if yes then is it a threat

Yes they do and they may not a threat to us. A black hole occurs when a star becomes old it dies or explodes known as a supernova. After that it shoots out destroying galaxies and then sucks back in causing a black hole. Our sun is still young so this will not happen to us any time soon, as for the surrounding stars around us I can't be sure but I think they are too far away to cause damage.

A 'black hole' is not named very well, since it is not a hole at all. It is just a star that is so big, that when it runs out of fuel and collapses, its gravity is so strong that light can not escape from it. So we can not see it. Over billions of years, at the center of the galaxy, some black holes have merged and have become very large. Their gravity affects everything in the galaxy because everything in the galaxy is in orbit around the center of the galaxy.

If we were to travel near a galaxy in a space craft, we would have to be careful not to get too close, or we would fall into it and be crushed.

:-D There are no black holes near us. So, they don't pose a danger to us. They are dangerous to anything that is near to them. On Earth, crossing the street is far more dangerous to us.

No blackholes do not exist. They are an irrational mathematical object made by dividing by zero to create a singularity. No one has ever observed a black hole except for the energetic jets of plasma coming from them LOL

Yes but the nearest one is very far away.
There is now believed to be one at the center of our galaxy and at the center of most galaxies.

Yes they exist and no they are not a threat. They are as much a threat as an active volcano or whirlpool, as long as you do not get too close to one you are not in any danger.

Yes, and they have been a threat for 15 billion years, and haven't gotten us yet. Worry about gas prices instead...

Yes they exist, no they are not a threat.

The only black hole i know about is the one where my anus is!

Lol DDD