I always have difficulty choosing the correct option from the following type of sentences
Option A: The defenders could have done more to prevent the goal that cost them the match.
Option B: The defenders could have done more to have prevented the goal that cost them the match.
I would go/stay with Option B, past forms "have done/to have prevented.
I also have difficulties choosing the correct option from among sentences of the types shown below; for example, which is the best option for a boss to use in a welcome e-mail to a new employee if they know that they won't be there when the person starts?
Option A: I would like to have welcomed you in person.
Option B: I would have liked to welcome you in person.
Option C: I would have liked to have welcomed you in person.
If the person has not yet started ("when the person starts") "I would like to welcome you in person, but unfortunately.....".
If the person has already started , Option C.
I would be extremely grateful for any help with/explanations on these.