I'll be honest, I'm seeing a lot of red flags here.
1) How do you know that this is what you want to do with no shadowing, clinical experience, or volunteering? The idea of being a physician and helping others sounds nice, but the reality of it is that it is a grueling process requiring many sacrifices with often thankless work. There's a reason why there is such a high rate of physician burnout and suicide.
2) Trying to pursue medical training while you are suffering from severe depression is an absolutely terrible idea. You need to make sure that your depression is completely under control before pursuing this career. As is oft said on here, medical school is a furnace that can break even previously-healthy students. I also wonder whether your sudden shift to pursue medicine now is a 'quarter-life crisis' or a consequence of your unmanaged depression. The decision to pursue medicine should not be made lightly, and demands a thoughtful and honest discussion with yourself. Again, it's not all rainbows and sunshine.
3) Can someone get in with just one year of activities? Sure, maybe (but not at my school). When someone suddenly starts volunteering a year before their application, that's a pretty sure sign that someone is just checking off boxes rather than being genuine in their pursuits. The more longitudinal your experiences, the better. The more hours you accrue, the better. There is no magical cutoff, but 200 clinical hours, 200 non-clinical volunteering hours, and 50 shadowing hours is a reasonable start.
4) The sooner you start the better (see point #3). Hospice volunteering and working with patients with late-stage dementia are both excellent clinical experiences to 'test the waters'. If you are truly passionate about these activities, you will make time for it. And if these experiences are too tough for you to handle, then consider it a strong sign that medicine may not be for you.
Just my honest thoughts.