Have you bought ------- for Linda's birthday?

这个句子要问的是你有没有买些特别的东西送给Linda做生日礼物,
have you bought .这个是一般疑问句,本来后面可以跟 something 也可以跟anything,但是按照语境,这里用something;因为用anyting 的话强调的是有没有买东西（只强调有没有买）,这里用anything的话语法上也没错,但是显得有点僵硬,所以用something,
至于unusual放在something后面,是因为something是不定代词,形容词要放在不定代词的后面,即 something unusual.