Warning: long post as I have too much to say.
I am of the opinion that hormone blockers do repress cognitive maturity. Therefore any person taking them before the onset of puberty could continue in their beliefs about themselves until some time after the blockers cease. That is why the gender clinics preferred to start them after a specific Tanner stage. That has now changed so some children are prescribed blockers before the onset of puberty. Some parents press for that and are taking a risk because their child will not be cognitively mature enough to "know" they will continue to feel the same way in adult life. (Gillick competent). The children who are given blockers pre-puberty are those who have been seen by gender specialists from a much younger age. Still there is scope for these children to have desisted before adulthood had they not been given blockers. It is a gamble. Not one I would take as a parent. My child was at the end of puberty before starting blockers. Had they been younger I would not have agreed to it. Knowing what I know now, five years later, I would have delayed blockers further if I could go back. I know plenty will disagree with me and shout about it being wrong to force a child to go through the "wrong" puberty. Having a boy child presenting as transgender must be more difficult I know; their pubertal changes cannot be changed easily, some not at all. So I suppose it is easier for me to hold these views as my child is a female transitioned to live as male.
On the subject of whether anyone can become the opposite sex or gender; my opinion is no they cannot. They can take hormones and have any number of surgeries but it will not make them the opposite of how they were born. Their discomfort in their sex/gender can be alleviated by presenting themselves to the world as the gender they are comfortable with. Their discomfort and dysphoria regarding their body can be somewhat alleviated by surgeries. Just like plastic surgery it makes a person feel better about themselves, give you more confidence and thereby allow them to live a happier more fulfilled life. But that life is never going to be exactly how it would be if they had been born in their preferred sex. How can it be if they are dependent on hormone therapy for the rest of their life?
With regard to toys children play with, someone asked if there were any cases of transgender children who did not prefer toys which were specific to children of the opposite sex. My child always played with non gender specific toys but also with dolls occasionally in the early years; preferring toy animals, toy vehicles, soft toys, construction toys and lots of outdoor play. Lots of drawing, art and craft and games. So not any gender typical activities really. So when he told me he needed to live as male it was a surprise but not unbelievable. He had started his own "soft" transition around the age of 9 or 10 when he started to refuse to wear anything with pink in it. He said he didn't like pink. OK I could accept that. He then wouldn't wear dresses or skirts. That was acceptable, I don't like wearing them either, even though I do wear pink. Then he wanted short hair. OK lots of girls have short hair so no alarm bells ringing there. Those sort of changes carried on for a few years without any alarm bells ringing for me. Of course this was over five years ago before all the recent media interest in transgender children. I probably would have suspected something if it was happening in my family now. But back then I had never even heard of transgender children.
So these are my opinions. I am happy to listen to those of others too and anyone is free to criticise mine. I am not being transphobic in anything I say. To be phobic is to be frightened; I may worry about what life holds for my son but transgender issues/people do not scare me. I cannot ever understand how they feel but I can be respectful to them and how they wish to live. I hope I have not offended anyone by stating my views and opinions. I don't intend to.