EDIT: SOLO - 401K

Here's my situation:
S-Corp
W2 does not have elected deferrals
TDAmeritrade Roth 401k and Traditional 401k

I do not have an auto deferral set up on my w2's, so I made a few contributions throughout the year to my Roth 401k via Personal Investment account. Say 3/15/2017 for $5000 and 6/15/2017 for $5000. A Total of $10,000 has been contributed by me personally without "employer" sending it in to my Roth.

From an employer standpoint, Does any one know if i have to report the 2 personal contributions on my W2 via Box 12 Code AA?

Question 2, Being that I can contribute max $18,000. Can I make a contribution now in 2018 for my 2017?

Weather it's Roth or Traditional 401k, I'm still working the numbers, but it is to my understanding that i have until 3/15/2018 to make these contributions as long as I have made an elective deferral statement/form by 12/31/2017. Is this correct? And I am assuming I would just add this to my box 12.

And the 37,000 Employer Match would not have to be reported on W2 at all. Correct?