Is it necessary to pronounce "CH" sound instead of "T" or "D" before YOU in the following phrases:

Would (CH) you like to go?

I know that (CH) you were there.

I hear some people pronounce the same phrases with "CH" sound and in some cases with
the normal "T".

What would you advise?

And why do they pronounce them so?

And if the same thing happens before all words beginning with "Y" (YOUTH, for example) or not?

I heard some people pronouncing "CH" before YEAH.

For example, I FEEL GOOD (CH) YEAH.

Thanks in advance.

Appreciate your help.
The phenomenon you have observed is "glide absorption". The glide "y" is absorbed into the preceding consonant. (I have never heard it in "I feel good, yeah", but it applies to all your other examples. Be careful. Some of them are the "j" sound, not "ch".) The following may be helpful.

Type 1. t + y = t + sh = ch

When a "t" at the end of one word comes in contact with a "y" in the following word, the combination creates the sound "ch". The most frequent "y"-words that are seen in this context are "you", "your", "yourself", and "yours". The word "year" also can be seen in this context.

"Won't you help me?" > Won choo help me?
"At your service!" > A cher service!
"last year" > lass cheer

Type 2. d + y = d + zh = j

When a "d" at the end of one word comes in contact with a "y" in the following word, the combination creates the sound "j".

"Could you pass the salt?" > cou joo pass the salt?
"Did they find you?" > did they fine joo?

In brief, Type 3 is s + y = sh and Type 4 is z + y = zh

Glide absorption between words is not required but most people use it all the time. It is a natural phenomenon in spoken English. In my opinion, you will never speak authentic English unless you master glide absorption.

Note that within a word (as opposed to between two words), glide absorption is almost always required:

nature = nate yure The "t" joins with the "y" to form "ch": na chure. (Type 1)
pleasure = plez yure The "z" joins with the "y" to form "zh": ple zhure (Type 4)

Note that the "u" is pronounced with a glide, so is effectively "yoo".
The use of 'ch' before 'yeah' is sometimes done for deliberate effect. I find myself doing it on occassions but only with certain people, it is a habit I think I have picked up from my teenage son and his friends. It is a sort of youth slang. I think British teenagers picked it up from a film called 'Wayne's World' - an American comedy with adults pretending to be 'rock' teenagers, (very funny film) that spawned a lot of 'catchphrases'.
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A great amount of respect to you both guys! Especially to CalifJim!