have been installed means now and had been installed means past
"TO" means to go to, to see. "IN" means to take part in, be part of
"What have you been up to?" means "what have you been doing?"
It means "What have you been doing lately?"
"Observed" is a word that means something has been noticed.
Have come to light means have been discovered.
It means that numbers have been skipped irregularly.
That means that it has been paid.
It has been a good time.
White smoke means a new pope has been elected.
It means it has been heated up to kill germs and bacteria, or it means that a metal has been treated to change its properties.
It means that that person was working the other one means they are working right now