Is there a way to book the below with miles?

PNH to SIN on SQ157 - economy
SIN to EWR on SQ22 - premium economy

I see both flights are available for my dates when selected individually. PNH to SIN is 13500 miles and SIN to EWR is 80500.

Can it be booked together as one award ticket? If so, what would the total mileage cost be?

Do i have to call in to book?

Thanks