[ChannelR]

Hey, I've been working my way through the JLPT N4 vocabulary, and I've come across a few things and I'd be grateful if someone could explain them to me. A few of them I managed to get figured out, but there are still a few things I don't understand.

頼む, 尋ねる and 聞く all mean to ask, according to my dictionary. When and where would I use each one?
使用する, 使う and 用いる all say 'to use'. 
親 and 両親 for parents.
返事 vs 答 for 'answer'

Also, the last time I was in a ramen restaurant, I didn't understand what she said when she asked if I wanted it hot or cold. I could have sworn she said いくら when referring to the temperature, but isn't that reserved for only asking price? Or can it mean temperature too?

And lastly, is there any useful tips for working on accent? When learning languages, a small worry of mine is an awful gaijin accent.