[Grammar] about article

They mean the same thing. However, to me, the first one is too general if not wrong and the second one is correct.
The second one uses "the.... of" structure. It makes the noun-English alphabet, more specific and defined.

玟聰：
2) The 26 letter English alphabet is based on( or originated from) the letters of the Roman or Latin alphabet.


It appears to me that only sentence No. 2 is correct simply because the sentence is talking about some historical facts of origin of the 26 letter
English alphabet, thus a Definite Article ,i.e., the, must be added respectively before ' 26' and ' letters' to indicate that we are talking about that particular 26 letter English alphabet and that particular letters of the Roman or Latin alphabet.

Basically there is no difference between the two sentences except the writing format.

However, we do not say 26 letter...... or the 26 letter...

We should simply say.

The English Alphabets are based on Roman or Latin alphabets.