Hyper Beam
no. u can use a TM once and HM as many times as you like
Three of them is the best. But the onnly thing you should know is: Their Moves. It is important to teach them TM/HM Because If you choose the wrong TM/HM your Pokemon will eventually become weak.
It is an HM.
The TM and HM case are given to you automatically when you get a TM or you get an HM. You can get TM THIEF in Mount Moon and HM SURF in the S. S. Anne. To access your TM/HM case you need to go to your BAG and it is one of the options in your KEY ITEMS slot. The name is in BLUE letters you can not miss it :)
Dive is an HM, but in Diamond,Pearl, and Platnum, it is a TM
flash isn't a HM it is a TM
Yes If you get the Tm's, surely the Hm's will be Right behind them
Eruption is not an HM it's a TM. Ask there the TM is or find a walkthrough of the game on the internet.
In Pokemon Platinum, Flash is a TM.
HM Flash
with TM and hm's
no its a hm