Is it rude to tell my BF i don't want just the necklace he bought me 6months ago for my BD gift?

no it isnt rude, but keep in mind that a gift is simply that, a gift, and that it is unconditional (meaning nothing is expected before or after). If he wants to giv u something, let him, if he doesnt thn tht should be entirely up to him since its a kind gesture from him. U can mention it if u want but personally i dont find it to be very appropriate when u consider what a gift is. It isnt an obligation