photo resizing directly on edit page

Hi, all, and thanks. We know you’re all volunteers and are sometimes the brunt of alot of anger.
#1 – I post photos on my blog page. Sometimes I double click and get little white boxes at the corners that allow me to adjust the size visually, without having to trial-and-error guess what pix size to ask for.
Often, though, I can’t get them to come up, and no adjustment of double-clicks that I know of brings them up.
How can I reliably call up those size-adjustment corners?

#2 – I tell the edit page to connect a photo with the media URL, but later, it’s like I never put it in. It’ll say that no URL was put in. I’ll work with the one photos for an hour, back and forth, and it will keep erasing my order to use the media URL. I cut and paste it in the ‘custom URL’ slot, but don’t know what the consequences of it not linking straight to my media library.
Again, thanks for what you do.
Laura Stella Sitges