Kala Vatana (or black peas) is used in Maharashtrian cooking, but many of my non-Maharashtrian friends have not heard of it. It resembles black peppercorn, but it's a bean. It is little bit tough, so takes little longer to sprout and it's advisable to pressure cook.
3. If you want to go really authentic, roast a whole onion on coals, take the peels off and then use the onion is the masala - if you are planning to use onion as mentioned in note 2.