Is it true? As long as you know how to write the 26 alphabets(from A to Z), you can write all English words?

Yes, it's true.

yes

no because english has borrowed so many words from different languages. also, all the words in the english language aren't actually used, so you can't really write all the english words, because you would never use them

Affirmative! Knowing what they all mean might be the greater challenge, but what are Dictionaries for?

Well yeah... Unless you count the ae and oe, but they're not really used any more. Also, you need apostrophes for some contractions. Is this actually surprising?

no because english has borrowed so many words from different languages. also, all the words in the english language aren't actually used, so you can't really write all the english words, because you would never use them

No, just the official ones. Dialect words sometimes can't be written. Toon for instance. People will read the american word for (car)toon, but what i mean is the north english (scots) word for town

Yes, all words in english are formed with only those 26 letters. Unlesz you count words like "don't" but that is only a shortened form of "do not"

Yes it is true. English words do not require diacritical marks (accents) although these are sometimes used in words borrowed (or stolen ) from other languages. At one time, and perhaps still in Britain, combined letters were used for dipthongs "oe, ae, etc.) but this is no longer the case on the West side of the Atlantic. Printers also used some ligatures or combined letters (ct, fl etc.) but these are certainly not required. There are also a few signs $, %, @ etc that are useful, but not necessary for spelling any English word.