Is the only difference between the 4 port and 8 port hyper .21 engines the sleeve???

I don't know about hyper .21 but in general, the sleeve porting need to match the case porting. So it could be that the answer is no.

lol how do u post im new to this? i need to know if a .15 cv-x is better then a .12r ss engine ?? and would a .15 fit in my hpi rs4 3 type ss?

I guess you figured out how to post

As for which is better. My guess in the .12r ss. The .15 CVX is an older technology. The .12rss to what I read, have a 1+(?) hp rating and newer.

Not personally have an HPI but it should as the RTR package do come with .15