user66605: I am thinking to buy one of "ATTINY85 Development Board"...
Before buying I was checking details/Advantages of it.

First I thought this is just a breakout board & USB for power.
But, then found It can be programmed with "Digispark driver & board manager" directly by the USB.

I checked this Question: EBay “Development Programmer Board for ATtiny”
Someone said there: 

"While limited, this type of board can be useful for "blink an LED on
  USB command" type tasks"

 
My Main question is:

Is it really programmable withut any TTL/ICSP/FTDI extention?
If so, is it possible to program other AVR chip (Attiny/Atmega) with simple codes directly via USB...?
(with same method)

user4143: 
Is it really programmable withut any TTL/ICSP/FTDI extention?

Only if you use an ATTiny chip that has the "Micronucleus" bootloader already installed.

If so, is it possible to program other AVR chip (Attiny/Atmega) with simple codes directly via USB...?

Some can, but most need a bootloader installing. The ATMega32U4, for example, has a "DFU" mode, which is essentially a bootloader in ROM, that you can use directly over USB.  In general, though, the answer is "Not without installing an appropriate bootloader with some hardware programmer first".

66605: <p>I am thinking to buy one of "ATTINY85 Development Board"...</p>

<p>Before buying I was checking details/Advantages of it.</p>

<p><br>
<strong>First I thought this is just a breakout board &amp; USB for power.</strong></p>

<p><strong>But, then found It can be programmed with "Digispark driver &amp; board manager" directly by the USB.</strong></p>

<hr> 

<p>I checked this Question: <a href="https://arduino.stackexchange.com/questions/23996/ebay-development-programmer-board-for-attiny">EBay “Development Programmer Board for ATtiny”</a></p>

<p>Someone said there: </p>

<blockquote>
  <p>"While limited, this type of board can be useful for "blink an LED on
  USB command" type tasks"</p>
</blockquote>

<p><hr> 
My Main question is:</p>

<p><strong>Is it really programmable withut any TTL/ICSP/FTDI extention?</strong></p>

<p><strong>If so, is it possible to program other AVR chip (Attiny/Atmega) with simple codes directly via USB...?</strong></p>

<p><strong>(with same method)</strong></p>
 4143: <blockquote>
  <p>Is it really programmable withut any TTL/ICSP/FTDI extention?</p>
</blockquote>

<p>Only if you use an ATTiny chip that has the "Micronucleus" bootloader already installed.</p>

<blockquote>
  <p>If so, is it possible to program other AVR chip (Attiny/Atmega) with simple codes directly via USB...?</p>
</blockquote>

<p>Some can, but most need a bootloader installing. The ATMega32U4, for example, has a "DFU" mode, which is essentially a bootloader in ROM, that you can use directly over USB.  In general, though, the answer is "Not without installing an appropriate bootloader with some hardware programmer first".</p>
