1. It is not cold any more.

2. It is not cold any longer.
3. It is no more cold.
4. It is cold no more.
5. It is no longer cold.
6. It is cold no longer.

Are all the sentences grammatical?
Are there any rules about the position of 'no more' or ' no longer'?

#5 is the preferred usage.

However, #1 and #2 are grammatical.
The others are not appropriate usage.

Yes, all the sentences are grammatically correct. The phrases "no more" and "no longer" both serve the purpose of expressing the absence or end of a state or condition. While they can be used interchangeably in most cases, there are some guidelines regarding their placement in a sentence.

In general, "no more" is typically placed before the adjective or adverb it modifies. For example, in sentences 1 and 3, "no more" directly precedes the word "cold."

On the other hand, "no longer" is usually placed before the verb it modifies or at the end of the sentence. Sentences 2, 5, and 6 demonstrate this usage, where "no longer" is positioned either before the verb "is" or at the end of the sentence after the word "cold."

Sentence 4 follows a different structure where "no more" is placed after the verb "is" but before the word "cold." Although this variation may present a slight deviation from the general rule, it remains grammatically correct and conveys the same meaning.