It shouldn't. It's an American idiom.
Yes, it is an adjective. It means of or according to the alphabet (sequence of letters used in language).
Official letters are more formal written communication used for business. Personal letters are less formal and written between family and friends. The heading, salutation. body, closing and signature are different in each type of letter.
An official letter is written to convey official information and is written in a very formal way. Business letter conveys information of a business type and may not be quite so formal. Business letters can also be used to persuade, while official letters are used only to convey information.
The most formal kind of functional writing would be formal letters. This type of letter would be used in circumstances dealing with business matters or even when writing to a stranger.
It's a formal way of expressing regards, usually used in the beginning of formal "inter-departmental, ministerial, etc." letters. Extend here means give.
The only adverb that appears to be used is changeably, from the adjective changeable.There does not seem to be any formal word changingly.
A business memo is usually used to communicate with a company or organization. It is less formal than business letters.
Papal bull
Speeches.
Yes, postal letters are still used today, although they are less common than before due to the prevalence of electronic communication such as email and messaging apps. Postal letters are still popular for formal communication, sending physical documents, and for personal letters and invitations.
These letters unscramble to spell the word centripetal. It is an adjective used to describe something moving towards a centre.
There are generally three types of letters: personal letters, formal letters, and business letters. Personal letters are written between individuals for personal reasons, formal letters are used for official communications or requests, and business letters are used for professional correspondence within a business setting.