if the attendent guard not there, what should i do?

1, my fight from US get to narita airport at 17:00, what terminal is that? where to get the jrpass exchange? are these office still open? do I able to catching the shinkansen using JRpass to Shin Osaka this late? how late is the last one go to shin-Osaka from Narita airport?
2, if I using JRpass and get on the Nozomi train? do I pay the difference of cost or have to buy new ticket?
3, what is the attendent guard not there at the gate? how can i get thru the gate with the JRpass? what should I do on these case?
4. I arriving at 17:00 on Dec 26 at Narita airport and leaving on morning of Dec 31, and want to tour Osaka, Nara, Kyoto, Tokyo, well, only 4.5 days, what do you suggest the attraction should I go? look like each place would use 1 day, what is the best attractions travel within a day using the JRpass with Subways and with walking?
5, should I book hotel 1st or get there and book? reason is I worry that not able to catch the train that late to go Osaka after landing from Narita airport.