When I EV train my pokemon do I need to kill the same type of Pokemon continually or can I kill whatever?

Question

For example, if i kill 20 pikachus and then I kill a bidoof, do the ev points reset?

Answer 1

No. They are all added. The only way to remove ev's is with berries.

Answer 2

they are all added

Answer 3

If you kill 20 Pikchus you will get 20 EV's that pikchu gives and if you kill a bidoof then you will get a 1 EV that bidoofs gives so in total you will get 21 EV's so no it will not reset just that you will get 2 types of  EV's (speed and HP)