废寝忘食:
1.to forget sleep and food
例如：When deeply absorbed in work,which he often was,he would forget all about eating and sleeping.
2.Too busy to eat or sleep
例如：He was too busy reading to eat or sleep.
3.Neglect one's meals and sleep
例如：Absorbed in the work,he neglected food and sleep.
least of all would I lie to you.的意思是：我最用不着对你撒谎了.least of all的意思是“最不”
它是强调句it is the least of all that I would lie to you的省略句,并且least of all前置引起句子倒装.
would是will的委婉说法.