"dui bu qi" is like vt. u can say " wo dui bu qi da jia", something like that. and "hen bao qian" is often at the end of the sentence. and u can say " ni dui bu qi wo" means u do something that offend me. but we can't say " ni hen bao qian".

"dui bu qi" and "hen bao qian" are similar,both mean sorry sometimes we can say those two in a same sentence."dui bu qi,wo hen bao qian." the differences we can say "wo dui bu qi ni" ,but we cant say" wo hen bao qiao ni“ ,can only say" wo hen bao qian"

i guess they r similar meaning and both used in informal situation.if u wanna to express formally,u should say"shen biao qian yi'' or "qing nin yuan lian''.

similar， but "duibuqi" is more formal, polite and sincere; therefore, it can be used in a serious situation. “henbaoqian" is more friendly and humor.