what the difference between 'in' and 'at'.

English as a Second Language English Vocabulary, Grammar and Idioms
1

he was expect to read the letter at each performance.
he was expect to read the letter in each performance.
he was expect to read the letter on each performance.

2

All your sentences require capital letters for the ‘h’ in the word ‘He’.

at each performance: at some point before, during or after the performance.
in each performance: at some point during the performance, as a part of the performance.
on each performance: as ‘at’ or each time he performed.

3

Remember that this should read: He was expected.

Alan