Oh, dude, technically both are grammatically correct, but it just depends on when you're talking about uploading those files. "I have uploaded the files" implies you did it recently and it's still relevant, while "I had uploaded the files" suggests it happened in the past and might not be as important now. So, like, pick your tense wisely, man.
No. It is not a sentence, but a dependent clause.
Yes, 'for free', is grammatically correct.
"Not like that" can be grammatically correct, depending on the context.
Yes! That is grammatically correct!
This is not grammatically correct. The correct form is 'you do not know', or the abbreviated 'you don't know'.
The Kindle can read PDF files uploaded from a USB memory stick.
'What a drunkard you are' is a grammatically correct English sentence.
"That was wrong" is a grammatically correct sentence.
Yes, it is grammatically correct.
Yes, Almighty God is grammatically correct.
'Once photos are uploaded' and 'once photos have been uploaded' are probably both correct, but I would use once photos have been uploaded
Sure. It would also be grammatically correct to write He spoggled his nubbix on the goober. Grammatically correct and meaningful are not the same.