If the two ends $P$ and $N$ of a $P-N$ junction diode are joined by a wire,what happens?

Which of the following is correct with respect to the following statements? Due to diffusion of electrons from $n$ to $p$-side:
$I$. electrons are accumulated in the depletion region.
$II$. electron drift current is from $p$-side to $n$-side.
$III$. an ionised donor is left in the $n$-region.
$IV$. electrons of $n$-side come to $p$-side and electron-hole combination takes place in $p$-side.
Select the correct option from the following.

In a semiconductor diode,the forward voltage is increased from $0.5 \ V$ to $0.7 \ V$. As a result,the forward current changes by $1 \ mA$. The forward resistance of the diode is ....... $\Omega$.

In the given figure,a $Si$ diode and a $Ge$ diode are connected in series. What should be the potential at point $A$ to bring both diodes into forward bias?

If the potential barrier across a $p-n$ junction is $0.6\,V$,then the electric field intensity in the depletion region having a width of $6 \times 10^{-6}\,m$ will be $......\times 10^{5}\,N/C$.

The voltage $V_0$ in the network shown is