Can Jesus do any miracle if we ask him?

If it is his will. Jesus went to the pool of Bethesda in John 5 and he healed one man, but it says there were hundreds of people lying there. He never healed any of them. We can't force God to do something. Paul had a thorn in the flesh. He prayed. It was not answered, because God said there's a purpose.

So, where it is God's will, he answers. He does many miracles. But, if it is not his will, he will not do it. Sometimes we can't understand, but God has a wonderful purpose in everything.