modern language has deteriorated so it probably not necessary. Or, modern language is always subject to change and such change may become acceptable. Or, as putting a period here means it represents a diminutive of the original words Mister or Mistress. Or, take pride in the presentation of your letter because the person that you are writing to is worth it
No. It is not necessary to put a period/fullstop after the m, because the letter is not used as an abbreviation. Instead, the letter m is a symbol used to represent the unit "metres."
We put the period after the word Mr because it's an abbreviation for Mister.
No. You put only one period.
no spaces
Yes, it is common to put a period after "Mrs." as it is an abbreviation for "missus."
Yes you should always use a period.
No, you do not need to add an additional period at the end of a sentence that already ends with an abbreviation like Oct. The period from the abbreviation serves as the ending punctuation for the sentence.
No you do not. Info. is an abbreviation and therefore requires a full stop
No, you do not include a second period when a sentence ends with an abbreviation like "MD." Just one period is used to end the abbreviation and the sentence.
Well, there's supposed to be one after etc. but many people leave it off. It's pretty much widely accepted now, although you may want to leave the period on if you are writing a paper or a professional letter.
No, typically you do not need to put a period after "Ave" when using it in a sentence. However, if "Ave" is being used as an abbreviation for "Avenue" in an address, then a period would be used after it.
Yes - but it is usual to put it in capital letter - OT.