2002 Accord vibration when 50+ mph and br

i bought a 2002 Accrod from the dealer. front tires are new. rear tires have only 4 points and have edge wear. when going above 50+ and braking it vibrates and drive is not smooth.

is the vibration due to bad tires are need to check the alignment. also i see the streeling wheel little tilt.

i am ready to change the tires, but just wanted to make sure the reason.

Also is there any way to identify whether the timing belt is changed or not. Dealer told it was changed by the previous owner

Pls advice.