No, there is no guarantee that you will return to a former life through meditation. It depends on many factors. Usually, stressful and traumatic events from the past come to the surface more accessible than other memories. That's why people first tend to remember their way of dying but not exclusively. Personally, I only have a few memories of dying and I remembered some other traumatic events quicker than that (broken trust, abandonment, loneliness, and so on). I also tend to need a trigger before memories come to the surface (people from a former life or a similar situation that occurred in the past). I have done multiple self-regressions during the past years and sometimes I landed in situations that I cannot tie to anything familiar. I really don't know if those images/memories were 'real' or not, although they came through meditation. I just put those memories in a 'mental box', waiting for some more validation before I acknowledge them as part of my history.
As soon as there are emotions attached to those memories, I will take them seriously. Like I feel again in my current body the pain, despair, and stress that come with them. On a few occasions, I felt a kind of merging between the former and the actual me taking place. These are highlights in my personal opinion. Even if the entire memories would have been 'false', I was given great benefits from the experience.
When you do meditations by yourself, start with formulating some questions that you really would like to know about. It's not a certainty, but more like a guideline toward some answers.
Some people get their information mostly through dreams at night, others obtain their information by a kind of instant knowing. This depends from person to person. Seeing visuals is not everybody's strong part, so don't be too disappointed if it doesn't work out the first time. And to be honest, since I tried most of the guided meditations available on Youtube, I have done these a lot of times and... so many times that nothing came up. Just nothing at all. To me it tells me that just the simple fact of regressing is not enough, there must be a kind of trigger or necessity for me to know something before the box of hidden memories can be opened.