Can you please help me understand EV training in pokemon?

1. I'm not quite sure what you mean here. If you erase the EVs from some stats. with berries, then the stats do go down. If you just ignore them, and never EV train them, then they stay as they normally would, they don't decrease by themselves.

2. Ah, yes. My brother likes to ask this. He want to give his alakazam EVs in defence, to make it better. Perhaps this is the thing to do. But although they have very poor defence, if you EV train them to have 252 in sp. att. and speed, this low defence is not too much of a problem, as they are so quick and powerful to 1HKO.

3. Yes. But do you really have enough money to buy all those stat. increasing drinks like protein? I use EV reducing berries. There's nothing wrong with them, that's why they're there. They helped me to re-do my torterra's stats. after I completed Pearl and learnt about EVs. Anyway, you can only use a certain amount of proteins etc, as I'm sure you know. If you have 0 EVs in attack, protein will only allow you to go up to 100 EVs. To be honest, in Diamond/Pearl/Platinum, the new items like Power Band and Power Belt help you to EV train very quickly, so I never use stat. increasing drinks.

4. EVs and IVs have always been encorporated into the game mechanics, but on R/B/Yellow and G/S/Crystal, there was no limit on how many EVs you could get (apparently). This was changed on R/S/Emerald so it was a maximum of 510, with 255 in each stat., as it still is now on D/P/Platinum.

Hope this helps you figure this out. I had these questions about this time last year. Email me if you're still stuck.

EV is short for Effort Value . Every time your pokemon wins a battle and gets
experience it gains an EV point in specific stat? Which stat does the pokemon
give a point in? Well, I will not be answering that here, there is another
guide dedicated solely to that purpose and to post it would be a waste of my
time and theirs.

Okay, so each pokemon gives a point. What do these points do? Well, when you
get four in a single stat, that stat will increase by one extra when you level
up. SWEET! That means I can fight a million Bidoofs and give my Mewtwo 250,000
HP? Well, no, unfortunately.

There are limits to how many EV points you can get, and this is why people EV
train. Altogether, you can only have 510, and a single stat can only have 255.
Why waste those points in stats you are not going to use? My Gyarados doesnt
know any special moves, so why waste the points there? I will put them all in
to attack instead. Using EV points, you can give two stats a bonus of up to 63!

Also, just to save you some time, I will tell you that you should only put 252
EV points in to a stat, even though you can put three more. Why? Because 252
is the largest number divisible by four that goes in to 255. So you would waste
3 Evs. Unfortunately, you can not stop some waste, and the EV spread people use
the most is 252 in one stat, 252 in another, and 6 in the last. This has the
minimal amount of waste.

So I have to fight 252 of a certain pokemon... ok... that sounds like a lot.
Well I have some good news for you! There are ways to speed this up. There is
a rare condition your pokemon can get called POKERUS. This does not harm your
game or your pokemon in any way, it actually doubles the rate you earn EV points
at. There is also an item called the MACHO BRACE that double them again. So
each point is actually worth four. Saves a lot of time, eh?

There are also the power items that you can buy at the battle tower. I will try
to explain them. Each item adds four to the EVs you would already be getting.
So if you fight a magikarp, and have the power item for speed, you get five EV
points. In case you have the POKERUS at the same time, you add first then
double. So these are even faster then the MACHO BRACE.

1. no....they stays same but the increase as u level up......
2. well....... no..... it actually depends....... for endure special hits u need sp.def and physical hits, def........... and pokemon gets their natural start/ev when they lv up.
3. lol.... it may......
4. didnt get wat u mean......... if u mean.... in wat game this EV training started then I will say.... ruby and sapharie.....

1. no....they stays same but the increase as u level up......
2. well....... no..... it actually depends....... for endure special hits u need sp.def and physical hits, def........... and pokemon gets their natural start/ev when they lv up.
3. no.... it may......
4. didn'tget wat u mean......... if u mean.... in wat game this EV training started then I will say.... ruby and sapphire....