Amide is NH3
Amine is NH2
No. It would take you
seconds to google that.
As far as numbering goes, compounds are generally named to give the lowest possible numbers in the structure. So, 6-methyl-1,3,5-trinitrobenzene and 4-methyl-1,3,5-trinitrobenzene are exactly the same as 2-methyl-1,3,5-trinitrobenzene, but the latter is preferable because it keeps the locant numbers to the minimum.
If you have a choice because the locant numbers for two names are the same, for example:
1-chloro-2-iodobenzene vs 2-chloro-1-iodobenzene
Locants are 1 and 2 in both names, but the first one is chosen as it gives the lowest locant to the first substituent alphabetically.
Note that if you have:
4-bromo-2-chloro-1-iodobenzene vs 1-bromo-3-chloro-4-iodobenzene
The first name is chosen because it gives overall lower locants (1,2,4 vs 1,3,4) - the lower locants win, even though it means the first substituent alphabetically does not take position 1.
These are brief rules, things can get more complicated so it's better to look at them on a case by case basis if you have any more specific examples you'd like explained.