Is it obligatory to make up prayers and fasts for a wet dream at the age of ten or eleven, without recalling seeing semen or pre-seminal fluid, and without the appearance of physical signs of puberty?

Merely seeing oneself practicing masturbation in a dream, without the emission of semen, is not considered a sign of puberty. Therefore, there is no need to make up for missed fasting or prayers for that period unless you are certain that puberty occurred then. However, if you are unsure, there is no obligation to make up for them, because the default is that one is not held accountable (for religious duties).