Is there a site that tells you if what you have typed is grammatically correct ?

Answer 1

The fastest would be Microsoft Word, but even then you have to be careful, as sometimes the advice does not make sense.
If you use it, make sure to exercise common sense, too.
If you need a source for basic grammar rules, there are tons of resources. You can either buy an inexpensive guide book, or do a search on the internet and copy them off. Not hard at all.

Answer 2

Yes

Answer 3

Dictionary.

Answer 4

yes ms word