hey i need to know ...
if i invert my sub .. do i need to switch phase
and my sub has a vented pole peace how far away from the back off the boot can it be .. does it need air space or something ?

since there won't be any other speakers for the sub to be in phase with, you won't need to switch the phase..

Generally 1-2" behind the vented pole piece is a good idea to allow it to help cool the coil.. The other issue, is having the sub right up against the back may not be optimum as far as loading goes.. (depending on the depth, as well as the note used, amount of SPL etc) Testing would be a good idea to know for sure..

when the sub is not inverted .... i have it around 16 cm away from the back ... when i have it inverted ... the pole peace is right on the back .. but the box is still right on 16 cm away from the back ... and if i movie it back a lil more it dont work as well ..... it's only for 2 second's .. it wont get hot that fast will it ? .. so what im asking is ... if the pole peace is right on the back apart from not cooling as fast will it affect my SPL