Do the same thing in Pokemon peaRL
You can buy TM70 Flash at the Veilstone Department Store.
you get the HM Flash after beating the electric gym leader, if i recall correctly
There is no HM Flash on Pokemon Diamond, I personally think its been replaced by HM05 Defog.
You get Flash from the Hiker in Oreburgh Gate. Alternatively, you can buy it in the department store over at Veilstone.
In Pokemon diamond many Pokemon can learn flash for eg. Electric Pokemon such as Pachurisu Pichu and Luxray all (eveloutions) and yeah just experiment and see what can learn flash!
You can purchase Flash in Veilstone City in the mall in Pokemon Diamond.
You can find Pidey in a Pokemon Outbreak in Pokemon Diamond
no
At the Veilstone department store (TM90).
It's not a HM anymore in Pokemon Diamond and Pearl, but it can be bought as a TM in Hearthome City Department.
the hiker is in mt.cornet
Nope.