Nowhere in The Bible does it say that blackmail is wrong. Blackmail is a threat to publicise an embarrassing secret (or an offer to remain silent about this information) along with a demand or a request for funds or other valuable considerations. Blackmail is therefore a threat to commit the sin of gossip unless paid off not to do so.
Threatening to gossip (or offering to pay to stop the gossiping) is not the same as gossiping, though. The blackmailer is offering or being enjoined to not commit the sin. In fact, the blackmailee is in a far better position with a blackmailer willing to sell his silence for a fee than in the hands of a gossiper, who will "let the cat out of the bag" no matter what. From the point of view of the backmailee, at least the blackmailer has the decency to allow him to buy his way out of being exposed; the gossiper offers no such consolation1.
1 Walter Block: Defending the Undefendable, p. 53 (Fox and Wilkes, 1985).
If you are following the Bible and open about your sins, you have no exposure to blackmail.
No. Go to allcreatures.org - link is below, under 'Related links'.
Mark 11:25,26
If you are talking about the Bible, it doesn't say that anywhere.
Well...the last time that I checked, the bible was written about 2,000 years before the invention of films, so I would say no.
It is illegal.
that's its wrong and it should not be used
Blackmail is a criminal matter, and I doubt that this rises to that level.
is it against god to buy a dog
There is much dispute amongst scholars in interpreting the bible's content. There is nothing in the bible attributed to God which, in every reasonable interpretation, is objectively wrong. (I am only familiar with the Old Testament, and cannot speak for other bibles.)
Depending on the context, blackmail is already a verb. For example "to blackmail someone" is an action and therefore a verb.
I believe it is just blackmail money. The act is called blackmail or extortion, and is illegal especially if paired with a specific threat.