Bird box behaviour

[stuartmmcfc]

Last year I put up a box with a camera in.
About 3 weeks ago a Blue tit started staying in every night.
A few questions have occurred to me

Can I tell if it s male or female?
What would happen if another bird fancied it as a sleeping place? Or is it first in”?
If it brings a mate back in the spring, will they both sleep in the box?
What about once the eggs hatch?

Thanks

[Orchid1]

Not relevant but this thread reminds me of this gem of a video

https://www.youtube.com/watch?v=YmyLagebU2k

[stuartmmcfc]

“Tweet” is much cuter than that,