I’m pretty up to par that to ‘Donk Bet’ is leading OOP after calling a PFR with a board giving us middle pair or believeing that the board has missed our OPP, am i correct? Are there other forms of ‘Donk Bets’?

Is this play in any means profitable and is it a tool we use in our arsenal?

There are situations you could do that if for example your opponent is very aggressive, you have been tight and the blinds big enough to be worth it the risks.

Overall, though, betting OP with marginal hands in NL is not good. Unless you are making a blocking bet. As usual, the answer is: “It depends”