Are the following sentences correct?
"What had i told you?"
"My tense is alright."
"As I had said, ......."
Welcome to the forum, Ananda Roy Chowdhury.
iI told you?" This could be correct. We can't say for sure without more context.
"My tense is alright." It sounds a little strange. Once again, only context can tell us if it's appropriate. Many people prefer to write 'all right', and some consider 'alright' to be incorrect.
"As I had said, ......." Yet again, we need context.