Quote from: ansdb on November 30, 2018, 03:54:15 PM

1- is the blocks can only contains one transaction or more ?

At least one. The block must have a coinbase transaction. The output of the transaction doesn't matter but the coinbase transaction must exist.

Quote from: ansdb on November 30, 2018, 03:54:15 PM

2- we know that the miners doing calculation through POW ? is it the same calculation of the hash tx ?

They hash the block headers which contains a wide array of data and the result is the block hash.

Quote from: ansdb on November 30, 2018, 03:54:15 PM

3- is the block that is created by a miner doesnt valide untill it is validated by all the miners in the network ? is that correct ? and how it is considered as a valide block ?

A block is valid if the nodes in the network think that it is valid. If the miner follows the protocol rules, then those who also follow the protocol rules should agree that the block is valid. If not, then they would be on a different fork since they don't accept that block while those who do builds on it.

The requirement for the block to be valid is quite broad, the crux of it is just that it follows the protocol rules which all of the reference nodes follow.

Quote from: ansdb on November 30, 2018, 03:54:15 PM

4- is every miner considered as Node in Bitcoin Network ?

Technically, it used to be. However, when pools came out, people found it more worthwhile to be mining together instead of separately. Most of the miners now don't run a node anymore due to the numerous benefits of pools.