Amount vs. amounts

hi,

do we usually say,

a copious amount of food OR copious amountS of food?

also,

for these sentences,

you were the last person I spoke with.

you are the last person I spoke with .

what's the meaning difference here (btw former and latter)?

and is it, spoke with OR spoke to ?

if both are correct, then, is there a meaning difference? if so what? (please try to explain even though it's subtle difference).

also,

what's the difference between,

1. It is no use crying over spilt milk.

2. It is of no use to cry over spilt milk.

3. it is useless to cry over spilt milk.

I know they all mean the same thing, but I am sure there's subtle/nuance differences between them in terms of when we use, purpose of emphasizing etc. could you please tell me?

thanks in advance.