Cloud's car stuff

[Cloud]

some questions about structuring a loan and paying it off asap (note that I have not yet decided whether to keep my present car too, trade it, or sell it myself):

1) Can I ask for my payments to fall within the second half of the month, regardless of the date I sign the paperwork?

2) What's the best way to make extra payments on the principal? Can I make any old extra payments I want? A little extra a month?

3) If I keep my car, and sell it myself later, can I use that money to make a substantial payment on my principal at that time without penalty?

I realize the answers may be specific to each lender, but loan paperwork is tricky! I want to know what to watch out for and ask.