It is said that greatest possible value of $380$ (2 s.f rounded) is $385$,and least one is $375$. How this is possible? if i try to round $385$ (2 s.f) it should be $390$. As the least possible value of $390$ is $385$.
How can i resolve these issues?
On
It seems that some people use a different convention for rounding when there is a "5." You seem to be using the "round half up" convention, but some people use the "round half to even" convention, under which you would have both $385$ and $375$ rounding to $380$. See this Wikipedia page.
Any real number $x$ satisfying $375\leq x<385$ will round to $380$ when being rounded to two significant figures.