Hi! 2,4,5 and 7 are incorrect. Am I right? Thanks, Fulvio

1. It is cheaper.

2. It is more cheaper.

3. It is much cheaper.

4. It is much more cheaper.

5. It is more cheap.

6. It is the cheapest.

7. It is the most cheap.

yellowstarstruck2,4,5 and 7 are incorrect. Am I right?

Yes, but 5 and 7 are not very serious mistakes.

The mistake gets more serious when a noun follows, because then 'more' doesn't modify the adjective. It modifies the noun.

more cheap merchandise = a greater amount of merchandise that is cheap
(not 'cheaper merchandise')