Are there 18 levels in hell?

Answer 1

As per Abhidhamma (3rd Pitaka of Dhamma), there are 08 main hells. There are 16 'mini' Hells surrounding each of these 08 hells. There is a darkness Hell, a river like hell and a tree like Hell!So, (8x16)+3= 131

As there are 16 mini hells [4 mini hells in each of 4 directions] surrounding each main hell, it is [8 x 16 = 128] mini hells. (remember that's only mini hells total)
Adding them to the 8 main hells, the number becomes [8 + 128 = 136].
The structures or kind of tortures in those hells should not add up here because we are calculating number of hells; not type of hells.
And yes, this is according to Buddhism. However, it's not from Abhidhamma Pitaka (The Profound Doctrine); it's from Devadūta-sūtra, Bālapaṇḍita-sūtra and Abhidharma-kośa. The Abhidharma-kośa is a book written by a Tibetan monk; and used by Mahayana Buddhism and Tibetan Buddhism.
It is said that there are 16 main hells { then it's gonna be 144 or 272 hells total }
The 8 hells (found in Majjhima Nikaya - 130th discourse):

1. Sañjīva (Hell of Retributive Justice)
2. Kālasūtra (Hell of Black Thread)
3. Saṅghāta (Hell of Crushing)
4. Raurava (Hell of Screaming)
5. Mahāraurava (Hell of Great Screaming)
6. Tapana (Hell of Burning)
7. Pratāpana (Hell of Great Burning)
8. Avīci (Great Hell of Ceaseless Torture and Sufferings)
The 8 cold hells (found in Nirvāṇa-sūtra):
1. Hahava
2. Atata
3. Alala
4. Ababa
5. Utpalal (Blue Lotus)
6. Padma (Crimson Lotus)
7. Kumuda (Scarlet Lotus)
8. Pundarika (White Lotus)
The 8 cold hells (derived from some sources):
1. Arbuda (Chilblains)
2. Nirarbuda (Chilblains Bursting)
3. Aṭaṭa (Chattering Teeth)
4. Hahava
5. Huhuva
6. Utpala (Blue Lotus)
7. Padma (Crimson Lotus)
8. Mahāpadma (Large Crimson Lotus)