I am doing my first ever International MR next weekend all on UA metal.
IAD-NRT-GUM-MNL-GUM-HNL-IAH-IAD

I think I've got everything figured out except for MNL. Technically it is my "destination" and I will be there for 12 hours (arriving in the am & departing in the pm). Will I be able to stay airside? or will I have to go landside and then re-enter. I read somewhere that I could not check in until 3 hours prior to my flight, so I am worried about getting "stuck" outside of security and not being able to access the lounges.

I have *G & Priority Pass, so it looks like the Miascor Lounge is my best option.

Any advice or pointers?