Some EV Questions in Pokemon Emerald

[E.C.A.M.B.S.]

So I've gotten back into playing Pokemon Emerald and I'm training up a team to beat the Battle Frontier. EV training is going well, but I have a few questions.

1) I was training my Beldum's Defense stat by defeating Cascoon. With the Macho Brace, that training amounted to 404 EV's. My question is, if I keep training a stat even after it has the maximum 255 EV's, am I wasting EV's out of the total 510 I can gain, or am I just doing nothing?

2) Now, I have 255 EV's in my Beldum's Attack and Defense stats. Does that mean that, now that I've completed my EV training, I can battle any Pokemon I want for regular EXP? Will I still get my +63 stat points if I do? Or do I have to keep defeating Cascoon and Poochyena till Beldum (Metagross) is lvl 100.

[Richard and Blaziken]

Training EVs in a stat beyond 255 does nothing, it will not waste any EVs.

Once EV Training is finished, you can battle anything, your EV Training is completed.

[E.C.A.M.B.S.]

Once EV Training is finished, you can battle anything, your EV Training is completed.

Oh thank god... I'm free.

Thank you, Richard and Blaziken!