Activating Japan Sim Free Iphone While on International Roaming

I am based from the Philippines and bought my sim-free iPhone6 Plus via online Apple Store and had it shipped to a Japan address. I will be going to Japan next month to spend my vacation and will get my iPhone as well. I understand that a sim free iPhone will be locked to the first sim that you will insert into it. I would like to ask for answers on the ff:

1.If I use my local sim (PI based) and activate my iPhone while on international roaming, will that lock my phone to my local sim and use it like a normal phone when I get back home?

2. Is phone activation while on international roaming recommended or will I need to wait until I get back home so I use the local signal?

Thanks!