I'm the battle frontier anon that posted yesterday or 2

>>31904299
No, they'll get their EV boosts at any level, you just have to either:

A. Level them up
B. Put them in a PC

Before they gain the stats.

>>31904484
I'll try to deposit metagross when I'm done with him.

>>31904299
Ah yes, I do know that lv100 mons don't receive the EV benefits

>>31904522

Only prior to gen 4

Box them and their stats will refresh

>is it true that the mons get their EV boosts only at Lv. 100
Actually, the reverse is mostly true. Due to way stats are calculated, a Lv. 100 mon will have its recalculated only if put into the PC Box.

>>31904299
It will only get its full boosts at Level 100.

When a Pokémon levels up with EVs, it gets [Level]% of accumulated EVs. If it was at Level 49, didn't have any EVs before and you maxed out its attack before evolving, it would gain 32 stat points in its attack (plus whatever it would normally get) upon reaching Level 50.