Help with parts identification from arduino starter kit from aliexpress

Those are tilt sensors. The rattling is a metal ball that contacts two pins inside, closing the connection.

The 1838B is a full module that partially decodes the received IR so that a MCU can fully decode the rest easily. What you have there is a bare phototransistor with an IR window on the top. You would use it for proximity or presence sensing. Instead of varying its resistance, it varies the amount of current it will pass.

Probably the single-digit 7-segment display, as opposed to the 4-digit display they have listed as "4 digital tube".