not at all. Hi there is very informal and without any affection while dear is somewhat personal

This one is potentially confusing in spoken english, because it's not uncommon for english-speakers to mumble or slur their words so that 'Hi there' sounds like 'Hi dere'. (like you sound when you have the flu).So you might hear someone who sounds like they are saying 'Hi dear.' In practice I don't think anyone would say 'Hi dear' because 'dear' is a rather formal, old-fashioned term, like darling. So one might say 'Hello dear' or 'Hello darling' but probably not 'Hi dear' Hi there is a nice greeting, it has a little more enthusiasm and energy than just 'hi'. You can tell that it might have been a greeting in person, maybe with a wave. It is like 'hey there' which is specifically for calling someone's attention. 'Hi there' is a greeting, with a little of the same exhuberance.

hi there! it should be used for attract uer attention before start to conversation.

From my Oxford Advanced Learner's English Dictionary: there (especially spoken):used to attract sb's attention. Example:Hi,there! Hope this also helps.

Not at all. 'Dear' is a minor term of enDEARment. 'Hey there' is pretty much the same as just saying 'hi'.