Hello there, sorry I've not replied sooner. Been away.
Your first paragraph is correct.
Re the second question. No, I normally always have the card in the camera normally, but the camera memory can still hold some pictures.
Just to test again, I deleted the pictures in the camera after removing the card from it. With the card still out, I took a couple of shots of my cats.
These were not 'seen' by the Windows 10 laptop, but they were by the XP.
I put the card back in and took another twenty shots, all hi res'.
Plugging the camera into the Windows 10 laptop did not help me download them as the DCIM folder was not there it seems. Taking the card out and putting it the laptop card slot allowed me to see and download all the card pictures. However, I had to attach the camera to the XP machine to get the few pictures left in the camera's own small memory to download. Not a serious problem but a bit of a nuisance anyway. Thanks for your reply btw.