Is it true that blues music charateristilly uses blue notes altered (3rd5thand 7th)?

Ummm . . . it is true that Blues Music characterisically uses, the minor pentatonic scale. altered.

The common blues scale is derived from the usual scale (1,2,3,4,5,6,7,1) by removing the 2nd and 6th notes. That leaves you with the notes, "1,3,4,5,7,1" .

There's more to it, though: you flat by a half step the 3rd and the 7th. That results in the notes, 1, b3 (flatted 3rd), 4, 5, b7 - 5 notes in all.