I have a mass of 82Kg. Can there be a Blackhole of this mass? If so, what dimensions would it have? How long would it last?
Would would the effect be on the Earth if Ak84 suddenly became a Blackhole?
There are no known limits on the possible mass for a black hole. There are probably unknown limits, but the best guess for such an unknown limit is the Planck mass, about 2e-8 kg, a factor of four billion times less than your mass (though again, I stress that this is an unknown limit). There are known (but fuzzy) practical limits on the size of a black hole, in that it’s really hard to come up with some way to make one out of anything smaller than a star, but if you could make one, it could exist.
If you did somehow become a black hole, with your mass, you’d have a radius of about 10^-25 meters. The consequence of this would be a very large (but not Earth-shattering) kaboom: So far as we can tell, a black hole so small would evaporate nearly instantly, and the products of the evaporation would be equal parts matter and antimatter, and we know what that leads to. A major chunk of the evaporation debris (perhaps 90% or so) would be harmless neutrinos and gravitons, but even 10% of 82 kg packs one Hell of a wallop-- That’d be equivalent to about 200 megatons (the largest nuclear explosion ever set off was about 50 megatons).
There’s a handy calculator here:
http://xaonon.dyndns.org/hawking/
That calculator actually severely underestimates the luminosity, and hence severely overestimates the lifespan. That’s actually the luminosity per mode. When you’re just emitting photons and gravitons, there are only four modes available (corresponding to two polarization states for each), so the estimate isn’t too bad, but the hotter the hole gets, the more kinds of particles it can emit. For a hole this small, you’d be emitting not just all of the known subatomic particles and then a whole lot more, you’d also be emitting all of the known atoms, and even a great many molecules. The number of possible modes explodes combinatorically, and I’m not even sure how to estimate it any better than “instantaneous”.
Actually, I take that back. I do know how to estimate it. The problem is that if you take the standard calculations for black hole evaporation, and extrapolate them out to such a small hole, you end up with an evaporation rate far greater than the assumptions that went into deriving the standard calculations. The solution, then, is to look back to those assumptions and the reasons for them. In this case, the problem is that an event horizon absolutely cannot grow or shrink in radius any faster than c. So let’s use that to estimate the lifespan: That would give us about 4e-34 seconds as a lower bound. And since the standard calculation gives a result so much quicker, that lower bound is probably a pretty good estimate for the actual value.
You gotta love a place where people not only can answer impossible questions, but they keep track of the difference between “instantaneously” and “a trillionth of a trillionth of a trillionth of a second.” 
Need answer reallllllllllly fast! 
You know, maybe it’s just me and my persnicketiness, but I don’t think I’d want to live in a universe where a mass of my size could undergo gravitational collapse. So, for my peace of mind, the answer to the OP’s 1st question is “no”.
I’ve known posters who were black holes.