As for the final Halacha, Hacham David Yosef rules in his Torat Ha’mo’adim (Hanukah, p. 126) that one should preferably stipulate before lighting candles on eighth and final night of Hanukah that the status of Kedusha applies only to the oil that burns during the first half-hour. Then, if the candles burn for a half-hour or longer, he may use the leftover oil as he pleases. If he did not make such a stipulation, or if he did but the candles were extinguished within a half-hour, then he should collect the leftover oil after Hanukah and burn it separately. Leftover oil from the candles lit on the first seven nights should simply be used for lighting the subsequent night, which is permissible according to all authorities
From a shiur by Horav Eli Mansour http://www.dailyhalacha.com/Display.asp?PageIndex=1&ClipID=1559
Technically this should only apply to the amount of oil needed to light for the first half hour since beyond that is not a mitzva. However since a person does not specifically say this, we are machmir and do not use any of the oil. What about leftover oil from the bottle that was never used? The Biur Halacha says that this oil is not assur in any manner since it wasn’t in a lit glass
from http://www.revach.net/halacha/tshuvos/Leftover-Oil-Halacha-and-Minhagim/1503