when you use 'bu hao yi si' to start your phrase, it means 'excuse me'. when you put 'bu hao yi si' in the middle of your sentence, for example,'zhe yang zhen shi bu hao yi si'. It means you feel awkward or shamed in some situation. 'dui bu qi" equals to sorry or excuse me. it won't sound weird. you can use it in a flexible way.

another difference is when you talk to older people you should use duibuqi. if you talk to your friend,buhaoyisi is better than duibuqi. buhaoyisi is more informal

is there any difference between young and old age

dui bu qi mean you are wrong,=i'm sorry bu hao yi si mean is more informal ,= excuse me you can use dui bu qi take the place of bu hao yi si almost.But when you feel guilty about sb. you must say du bu qi.....

another world also use some thing like baoqin