300 premium is top of the line with alot of options n engine is 3gr 3000cc with afs,rain sensor vipers, auto parking,traction control on/off button,VSC, heated n leather seats cruise control electronic suspension for high speeds but u wont be able to find all these options in one car if yes price tag will be way off
250g has alot of versions it comes with 4gr 2500 v6 210 hp.
Yes sports version is known as s version it comes with all black interior and with almost all the options as 300g premium and 18 inch rims and s version has electronic shocks by putting it in sports suspension mode the steering becomes heavy and it looks like car is more sticked to road rest above options are in s version
On top of it x has the same transmission as 86 and gr has the best compression ration 4gr has a compression of 12:1
Any other questions please feel free to ask