Is liquid Minoxidil or foam Minoxidil more effective? Once or twice a day?

This needs an in-person evaluation. I suggest seeing a hair loss expert now to go over your condition and provide you information about your best treatment options. There are great non-invasive options like prp/progesterone which can help with hair regrowth and/or hair transplantation. See an expert. Best, Dr. Emer

Liquid and foam minoxidil are equally effective. For some people the liquid causes excessive oiliness  and inflammation; foam usually does not.

Minoxidil foam and liquid are equivalent but the foam is better tolerated. With more extensive loss, I often recommend the liquid over the foam due to ease of application to large surface areas.

Liquid minoxidil contains propylene glycol which helps it penetrate more deeply, but it does tend to cause more irritation and allergies than a foam version. The efficacy of minoxidil was based on clinical studies where it was used twice daily.  However, it is not uncommon for patients to use a larger dose once a day at night time. If the liquid version is not causing you any problems and you don't mind its messiness, it is probably a slightly more effective option due to its deeper penetration.  

I believe that the liquid than the foam bause more gets on the scalp where it is most effective while with the foam it goes the other way, more on the hair than on the scalp