all 4 casts, menstruating woman also should do ekadasi fast and no grains aon that day

 https://www.salagram.net/ekadasi-vratHBV.htm#:~:text=Any%20Vaisnava%20who%20knowingly%20or,not%20be%20happy%20with%20him.&text=Therefore%2C%20O%20best%20among%20human,observe%20Ekadasi%20overlapped%20with%20Dasami.

 From the age of eight to the age of eighty every one must fast on ekadasi

BRAHMANA KSATRIYA VISAM SUDRANAM CAIVA YOSITAM
MOKSADAM KURVATAM BHAKTYA VISNOH PRIYATARAM DVIJAH

(HARI BHAKTI VILASA 12/7 from BRHAN NARADIYA PURANA)

 Oh brahmanas, those of brahmanas, ksatriyas, vaisyas and sudras, whoever one may be, who fast on Ekadasi with full devotion, will certainly achieve liberation.

EKADASYAM NA BHUNJIYA NARI DRSTE RAJASYAPI

(HARI BHAKTI VILASA 12/16, Srngi Rsi speaks)

 Even if a woman is going through menstruation, she should not eat on Ekadasi.

 Oh king, one should never give up fasting on Ekadasi, even if it falls on Saturday, Sunday, on an eclipse day or on Sankranti day.