How is the theme of Parents and Children introduced in the first four chapters of Great Expectations?

I have edited your question to refer to just one of the several themes you mentioned: remember you are only allowed to ask one specific question at a time.

From the opening pages of Chapter 1 where we are introduced to a Pip weeping over the graves of his parents and siblings, the theme of parenthood is introduced as a vitally important theme within the novel and indicates how much of Pip's subsequent story will be determined by the substitute parental figures that surround him. It is highly significant that Magwitch, the escaped convict, pops up behind the gravestone of his parents, as if to indicate that Magwitch is one of these substitute characters that "fathers" Pip, as indeed we find out he does in the course of the novel by becoming Pip's benefactor. However, his parenting is flawed as his very first act is to terrorise Pip into committing thievery.

Likewise, other parental figures are introduced when Pip returns to his home. We are introduced to a cruel and violent parental figure in Mrs. Joe, who brings Pip up "by hand" and Joe, who is depicted as a concerned and loving father-figure, stands by whilst Pip is beaten, ineffective to truly father Pip. Meanwhile, during the Christmas dinner, Wopsle and Uncle Pumblechook make fun of Pip in a cruel, vindictive fashion, whilst Joe is only able to stand by and pour on more gravy onto Pip's food as an act of consolation.

In these first four chapters, therefore, the range of substitute "parents" that Pip has or is surrounded by are indicated by their lack of parenting skills - Pip is used and abused or not defended in the way a child should be, thus foreshadowing how he is "used" by other parental figures later on in the novel for these characters' own ends: namely Miss Havisham and Magwitch, but also pointing towards Pip's final reconciliation with the one parental figure that truly loves him for who he is: Joe.