can I charge Mobile battery using mobile charger directly?
This is an absolute no-go.


Not from the terminals on the outside of the battery, it is when
you open up the battery-pack.
Charging Li-ion batteries is mostly
current controlled, with cell-temperature, voltage (change) and
absolute charge as input parameters. A second (top-up) stage is
voltage controlled.
The battery should at al times being
monitored against such actions or a defective charger, however the
failsafe is not required to auto-reset.
Yes, See 2.
Yes, if you would succeed in direct charging the cells despite
safety mechanisms an overcharge will even be able to cause an explosion.