MAA KALI is the Supreme Deity of the Saktha religion.
Before going on to the details of Kali upasana, a couple of important points. Some of this may not be known to all.
1. MAA KALI has many Rupas, more than any other Deity in the Hindu pantheon. Ranging from Smasana Kali to Shodasi Kali (also known as Maa Lalitha Tripura Sundari). Not many may be aware that the Tripura Sundari temple in Tripura is Shodasi Kali. That is the local name. The state of Tripura is named after her. She is called Shodasi because of the Shodasi mantra (sixteen lettered mantra) with which she is worshiped.
2. Yes. Kali is worshiped in the SriVidya tradition also. There is a KramaDiksha for that. Medha Samrajya Diksha is the Purna Diksha.
3. Kali Upasana does not have any rigid rules. This is emphasized by all the Tantras. Kali is accessible to everyone irrespective of caste, creed or social status.
3. Kali Upasana ranges from the purely Sattvic Upasana to the extreme form of Tantric Agora Upasana.
4. Though many Tantras emphasize the so called Vira Sadhana, in real life it is seen that Maa Kali is pleased with all types of Upasanas. Though Sri Ramakrishna did learn Tantras fom Maa Bhairavi Brahmani, he did not worship Maa Kali in the Tantra tradition. He was a Kali Bhaktha and worshiped her with Bhakthi. As we all know Sri Ramakrishna was the foremost Kali Bhaktha in living history and had her Dharshan.