A: I don't blame you for being confused. The statement that Jesus made to Mary at the open tomb has been the subject of much confusion. But it all centers around the fact that Mary had lost Jesus once and she wasn't about to lose Him again. So when she finally recognized Him there by the tomb she grabbed onto Him and wasn't about to let go. So Jesus said to her, "Do not cling to me..." which means, "It's okay Mary, I'm not going anywhere." and then He went on to say, "I have not yet ascended to my Father." That's the phrase that people struggle to understand because on the surface it sounds like Jesus was saying He had not yet been to heaven. But in the Greek, this phrase refers to a STATE OF BEING rather than an ACTION. So, in essence Jesus was saying, "I have not yet entered into an ascended state."
Jesus was planning to spend the next 40 days (off and on) with the disciples before finally entering His final "ascended state." So He was communicating to Mary that there was no need to hold on to Him because His final ascension was still many days away. He was NOT saying that He had not yet been in heaven.
Incidentally, a lot of people are curious about what Jesus was doing during that time when His physical body was in the tomb. I believe one of the tasks He had during that time was bring to heaven those who had previously died in faith. We know that under the old covenant people did not ascend to heaven since "the way" had not yet been opened up. (See John 3:13). So, believers were taken to a holding place which Jesus spoke of in a story recorded in Luke 16 which He called "Abraham's bosom." (Luke 16:22) It was a place of comfort where they awaited the completion of our Lord's' work on the cross so that heaven might finally be opened to them. How incredible that must have been for our Lord to usher those folks into the never-removed presence of God!