They are acceptable.
Mr. Shusterman's (former INS Trial Attorney, 1976-82) response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.
They will accept handwritten documents. If you have access to a notary public who can verify the identity of the person who is handwriting the documents that is even better.
Generally USCIS will not extend deadlines. It is better to submit what you have and then submit more later, asking for permission to do so. If you absolutely cannot me the deadline, schedule an INFOPASS meeting and explain your situation.
I hope this helps.
This response is provided for informational purposes only. It is not legal advice and does not create an attorney-client relationship. Questions and answers posted to this forum are public and cannot be kept confidential. Although admitted in DC, I currently reside in Texas and I am authorized to practice U.S. immigration law worldwide..