Philadelphia Eagles Football Club, Attn: Community Relations Department, 1 NovaCare Way, Philadelphia, PA 19145.
Donation is the correct spelling.
Yes
Try, "I am respectfully requesting a stay on my decision."
That is the correct spelling of "bear with me", requesting "forbearance" or patience.
Yes, though to make it flow more smoothly, I would write "I have sent an email requesting that you be added to the list."
Yes, it is correct to write "Please reply by today" to indicate that you are requesting a response by the end of the day.
The correct spelling is 'Philadelphia'.
Address with double-d is correct.
"Was it your previous address?" is proper grammar. You could also ask "Was this your previous address?" or "Was that your previous address?"
how to write correct address on the envelope to Lithuania
The proper name, the largest city in Pennsylvania, is spelled Philadelphia.
The correct spelling is "address". When you are talking about more than one it's "addresses".