whiteman808 What are the necessary steps to do before flashing Graphene OS on new Pixel?
Carefully read and follow the all the steps here: https://grapheneos.org/install/web
whiteman808 Do I need to remove SIM from physical slot
No, you can leave it in, it won't make a difference.
whiteman808 r discharge and then charge battery to 100% to avoid battery reporting status issues?
No need to discharge. I would make sure there's at least 50% battery,. It wouldn't hurt to have it full charged, but it's not necessary.
whiteman808 Is it safe to flash Graphene OS on partially charged battery
Yes it is safe, but it'd make sure there's at least 50%.