That would be incorrect use of "standard" English grammar. The irregular verb "to be" is conjugated thus:-
I am
You are
He is
She is
We are
They are
Thus to say "you is" in a formal situation would indicate to the people hearing you that you either had a poor command of "standard" English or that you had been brought up in a particular ethnic community where this form was common.
That said the use of "you is" in that particular community is, to me and possibly others, warm, charming and endearing. Language evolves and grammar changes there are no absolute rules, try and adapt what you say and how you say it to get the desired response in/from your target audience.
It depends on the sentence. Here's a correct usage for it: "That must have beed the best day you ever had."
No, it is not correct to say "had went." The correct usage is "had gone." "Went" is the past tense of "go," while "gone" is the past participle.
The correct phrase is "Have you ever had." This is the proper structure when forming questions using the present perfect tense.
No. Best is a better word for your intended purpose. It would be more correct to say greatest christmas ever than great
no. the right way is, Have you ever been to Spain?
Yes! "She is with me and John." You can test it out by using the sentence with just one of the persons at a time. For instance, "She is with me." is correct. Also, "She is with John." is correct. Therefore "She is with me and John" is also correct. (However it might sound more natural to say "She is with John and me")
The correct form is "have they ever come." "Come" is the past participle form of the verb "come," and should be used with auxiliary verbs like "have."
It would be correct to say that it was a Portugese Colony for close to 500 years.
"In the future" is the more commonly used phrase. It refers to a general unspecified time ahead. "In a future" can be used if referring to a specific, hypothetical future instance.
Yes, "do do" is correct grammar when used in a sentence. It can be used as a noun to describe a toddler's excretion or as a verb meaning to perform an action twice.
NEVER. 'I seen it' is grammatically incorrect and sounds awful when spoken. Please - never, ever, ever, ever say 'I seen it'. The correct sentence would be 'I saw it'.
"Where ever" should be spelled as one word. "Wherever you are" and "wherever I am" are correct.
The sentence 'Lea's first green head band ever she wore' is not correct grammar. There is no verb (predicate). A complete sentence might say "Lea's green headband was the first one she ever wore."