Eg:
He Could ride a bike.
He could ride a bike at this movement.
He could ride a bike last morning.
He could ride a bike tomorrow.

What is the difference among thier meanings ??!!

Inglês (EUA)

they just add to the first sentence to make it more interesting i guess or it depends if you are asked a certain question

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Inglês (EUA)
Espanhol (México) Quase Fluente

Although they all seem similar, they are responsive sentences from questions like:
What can he ride?
"He could ride a bike"
In what movement can he ride the bike?
"He could ride a bike at this movement" and etc.
They are different because they answer specific questions, thus they are not same.

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Hindi
Inglês (EUA) Quase Fluente

Not Cleared, Will you please elaborate ?

Inglês (EUA)
Espanhol (México) Quase Fluente

I will try my best.
The sentences above were responses from questions. In a way they all mean that (he) is riding a bike but the difference is how he is riding it and when.

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Hindi
Inglês (EUA) Quase Fluente

Let me, explain my view, if somewhere I'm wrong, Please help me to improve.

1. He could ride a bike.
- Maybe he can ride today or Not. (there isn't any time indicator so we can interpret according to situation. )

2. He could ride a bike at this movement. (Present tense)
-He could ride a bike at this movement if he were here in this tournament.

3. He could ride a bike last morning. (Past tense)
- He could ride a bike last morning but he didn't Or may he isn't able to.

4. He could ride a bike tomorrow. (Future tense)
- He could ride a bike tomorrow if he will clear the entrance test.

uses of 'could' is right here in every example ?!!!

Inglês (EUA)
Espanhol (México) Quase Fluente

oh I see what you mean!!
I guess in this case "could" does not affect the past, present, or future. Its the detail after like "tomorrow", "last morning" and etc. the word "could" is used in many ways; they all mean the same. it's (as i said) what the detail after is what is important.
Besides that, you had a really good question!! I hope I helped somewhat.

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Hindi
Inglês (EUA) Quase Fluente

As you said, "All the mean is same, doesn't effect by tense". so what does that mean : is there any one-line definition of could that fits in every tense perfectly.

Inglês (EUA)
Espanhol (México) Quase Fluente

@GrvD hmmm.. I hope this answers your question. the word "could" can be used in phrases to indicate either tense like the present, past, or future, depending on how the phrase is constructed the responses can mean something specifically different.
That's all I got ahaha

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