Regulator

What is the function of the regulator in Arduino Uno ?
Does Vin pin has safety and is it related to regulator ?
What is the voltage that arduino can handle ?

The function of any regulator is to convert an unregulated input voltage to a fixed regulated
voltage. The Vin pin is the Unregulated Input
pin and is rated for 7.5 V to 12V input voltage.
The Arduino UNO has two regulators: 3.3V and 5.0 V.

You'll have to define the word "Safety" because
that is not an Electronics term.

What is the function of the regulator that is above the barrel Jack?
Is it related to the 3.3 v pin ?

raschemmel:
You'll have to define the word "Safety" because
that is not an Electronics term.

That's a good one.

HassanBosha:
What is the function of the regulator that is above the barrel Jack?
Is it related to the 3.3 v pin ?

Just look at the schematic- it's on the Arduino site.

Come to think of it, that's an odd question. Why are you asking?

Let me try: First safety is not an electronic term, it is understood as the number 1 REQUIREMENT!

The input voltage typically 12V but has a range from about 7V to 21V is applied to the five volt regulator which supplies 5 volts to the board. The 3.3 volt regulator is fed from the 5V regulator. There are several reasons. If the 3.3 were connected to the VIN it does not have the input voltage range of the 5 volt regulator so it would reduce the input voltage range for the power. The power dissipated by the 3.3 volt regulator would go up dramatically if connected to VIN Hence it is connected to the 5V regulator output. Assuming a 150mA load on the 3.3V at 5 Volt input it consumes abut .25 watts, With a 20V input it would consume 3 watts. Hopefully that puts it into perspective.
Good Luck and Have Fun! Gil

You still have not DEFINED your safety criteria.
While "safety" is not an electronics term there are thousands of "safety components" all of which
have clearly defined criteria for there operation.
For example , light barriers that use leds to create
a criss-cross pattern to detect a human in order to shutdown a robot.
The question:
"Does the Vin pin has safety ?"
is meaningless without defining what you
mean by 'safety'. Without the criteria it's
just a word.
Now if you asked "does it have over-voltage
SCR crowbar function or reverse polarity
protection (diode) that would make sense,
but to ask if it has safety makes no sense,
to anyone with any formal electronics training.

Point being, "how safe is safe ?"