ok BLS removes correct?

I can remove but not ATK>
but can i

Atk then Remove in Main phase 2?
it says once per turn and turn is any phase right? so if i atk. then remove i havn't applied its effect yet? can i do this?

Think of his his first effect like Scapegoat's Summoning restriction. You cannot summon a monster during the turn you've played Scapegoat. If you Summon a monster BEFORE you play Scapegoat than you CANNOT play Scapegoat that turn. The same aplies to BLS-EotB's first effect. "If you activate this effect, this card cannot attack during this turn." means if you use that effect, at any point during this turn, you cannot attack that turn.

So that means i can't atk then use his effect in main phase 2?

no you can not basically the card is saying choose either to attack or remove. so if you attack you can't remove and vis versa