Is it obligatory to pray and fast on the two days preceding menstruation, during which intermittent brown discharge appears?

The brownish discharge before menstruation has two scenarios:

1. If it is separate from menstruation and not accompanied by pain or cramps, it is not considered menstruation and does not prevent prayer or fasting. However, it nullifies ablution and is impure. 2. If it is connected to menstruation or accompanied by menstrual pain and cramps, it is considered part of menstruation and prohibits what menstruation prohibits, just as if it occurred at the beginning of menstruation or was connected to its end.

Therefore, the brownish discharge you mentioned that appears before menstruation is considered part of menstruation due to its de facto connection to it.