Most of the time I work a solo dev at the companies I've been in. Which to be more specific means, maybe I'm not always the only dev in the company but more often than not, the only dev in a project. The big exception was my remote job of over a year, where all the devs worked on the same project.
A lot of my correspondence involves talking to non-technical people such as project managers, so I have gotten to figure out how to communicate many things to non-tech people.
1) I usually don't. Unless I really bombed on a problem and am stuck on solving a problem for so long, I really can't tell true negatives from false negatives by the tone of someone's voice, or what they say to me.
2) I apply to mid-level jobs. I used to apply to senior positions (have held 5 jobs) but as I'm getting so many rejections, I've lowered the bar since.
Going by the phrase, "walk before you run" I consider myself still in the walking phase for many skillsets, yet even if I apply to jobs that are less challenging to get into, many people assume I have enough experience to run and say I cover lots of ground but not a lot of depth to have an exceptional strong point. And this is coming from someone with a lot of experience in small companies, where "running" is the norm. I thought years of experience is just a number? Many people learn at different rates, and have a diverse set of work histories.
3) I do some research in questions I should ask, and what I should know about the company beforehand. Typically would be able to find some work they're doing and bring it up.
4) My go-to questions to ask interviewers is "how long have you been working at this company and how have things changed since then?", "What is a typical team size for engineering/development?" and "What is the onboarding process like for new hires?"
5) Interview practices are almost impossible with a friend because I don't know any close friends in the industry, or with any experience interviewing people in general. More of a homebody so I don't talk to many of them. Because of that, I don't believe a mock interview with a random friend is a good substitute for a real interview, because they will not have actual experience in hiring developers.