front wheel size 18"x8 +30
rear wheel size 18"x8 +30
front tire size 225/45/18
rear tire size 245/45/18

 

yes
yes
yes
yes

you're better off running the same tire sizes all around considering it is the same size wheel all around AND it'd be easier to rotate.

 

Yes you may run your car with those tire types and moreover fit correctly until it junk and its good choice to do the alteration.

 

x2

i had those sizes on my car and it was pain to rotate, plus why would u want to to that? the car is not not rear wheel drive

 

yes you could run all those sizes but the tires are too large. the overall setup is bleh tho, not sporty by any means.

 

Yes you can run these tyre sizes in your i30 . i have one of them installed in my i20. with this turning of the car becomes difficult. be sure of that .. http://www.ceattyres.in/ this link might help in solving your quest further

hope this helps
Thanks