hi, can i use 433 routerboard with 3 radio card for 3 sector antenna 2.4 ghz ??

yup,

it is always better to use different frequency band

You can. I've done it. I recommend against it.

Self interference.

That being said, MMCX cards are suppose to be better about the interference issue, but I haven't verified this yet.

If I were you I would go with the highest 711 board or a 411AH with your wireless card of choice. We are in the process of separating all our units into one card per board. Network just seems to run better that way.