JR Pass Reservation (Osaka-Kyoto Return) (Osaka-Tokyo Return) (Osaka-Hiroshima Return)

Hi there,

I have booked a holiday in Japan, April 26th-May 9th and intend on using the Shinkansen during my time there, I will be based in Osaka. Is it possible to reserve seats one month in advance on the Shinkansen routes which start from Osaka? Or are reservations limited to certain rail lines?

Thank you.