a) If one’s parents forbids them to fast Asara Bateves, Tzom Gedalia and Taanis Esther can one still fast?
b) what is the brocho for sushi?
c) If I have a cup of water and have in mind having a chocolate bar afterwards must I make another shehakol on the chocolate?
d) If I have a bag of crisps at break and the bell rings should I say a Brocho Acharona or can I continue eating them in another break without a brocho rishona but say a brocho acharona?
a) One can still fast. There is a rabbinic obligation to fast on these days, and one must fast regardless of parental advice. Of course, one should respectfully explain to parents that there is an obligation to fast on these days.
b) If there is a mixture of fish and rice, the berachah will follow the majority (usually, rice) – mezonos. If the two are not mixed, two berachos are recited (see here).
c) No, though it is preferable to recite the berachah on the chocolate.
d) Because you are stopping eating, and will only start again later, you should say borei nefashos at the end of the break, and recite another berachah (shehakol) later.