Check your application status
If it says "Under review" there's nothing to worry about
Otherwise, email the admissions department and make sure they got the LOR

Use a standard font like Times new roman and size 12

No, it will not.
But make sure you use the college/company letterhead to signify your recommender's authority.

Make one and use it for all
Just make sure you delete the author details from properties, though

Pen down your LOR in the standard format, covering all the aspects of a regular LOR
Once this is done, it should be easy for you to divide and edit your content accordingly
Reach out to me in case you need any help

Depends
If you're only applying to 2 or 3...
And if your recommenders are okay with it...
You can
Still, I advise against it

You can refer this blog to see how to write it