Physically, yes.
Mentally, no. His conscious doesn't want to kill a human being - it's just ethically wrong! But his wife, sees this differently.
why was macbeth releuctant to kill duncan
To inherit Duncan's Throne
She influences Macbeth to kill Duncan. Also makes Macbeth a stronger person. Later it is revealed that her tough personality is an act and that her conscience is killing her too.
NO! Lady Macbeth does not kill king Duncan's Guard Macbeth does to prove his guilt.
Lady Macbeth convinces Macbeth to kill Duncan by questioning his masculinity and invoking his ambition for power. She manipulates him into believing that murdering Duncan is the only way to achieve their goal of becoming king and convinces him that they can get away with it.
She gives him the weapon and the opportunity.
Macbeth kills Duncan in his own castle at night time.
The reaction between Lady Macbeth and Macbeth is initially very different after they kill Duncan. Lady Macbeth is enthusiastic but Macbeth regrets his actions.
It's not so much what she tells him, but how she needles him. She knows that he is sensitive to threats to his masculinity, because of the peculiar idea they have that masculine=courageous=good. So all she has to do is to say, "What? Are you not manly enough to kill Duncan?" and he will come around.
She didn't want to kill him herself, because she said Duncan looked like her dad while he slept. She did have Macbeth murder Duncan nonetheless
Macbeth believes he has to kill Duncan's guards in case they heard anything happen in the room while Macbeth was killing Duncan.
Well, it is Lady Macbeth's plan really, although Macbeth was tempted by a similar idea. The idea was to kill the king and put the blame on his servants. Macbeth is Duncan's cousin, and so might succeed to the throne.