They certainly know what a bar tab is and will let you run one. Better know the staff and trust them (or don't get drunk enough to lose count).
1. Not possible. 1 is an odd number and the answer must be divisible by 2, an even number. 2. I believe the answer to your second question would not be relevant due to the likelihood of your falling off your barstool before standing up. :pag komedya. Sent from my iPhone using Tapatalk
One factor in the misunderstanding: Flipino English does not recognize the indefinite pronoun a/an. So you think you have already specified "one", but you have not. If you order "one beer" rather than "a beer", the server will understand.
Problem solved..........it sounds a bit like the he/she mixup thing that happens with my wife. She gets that wrong about 50 percent of the time.
For newcomers, you are referring to the gender-neutral third-person pronoun in Filipino languages (all Western Malayo-Polynesian languages? I don't know). So that many Filipinos will use he/she interchangeably. English-language woke-ists have been struggling to create a gender-neutral equivalent, which made "them" used for the 3rd-person singular a "word of the year" for 2019.
Could it be the subtle way to find out if the tall, lean, handsome expat sitting in front of them is still available?