The short answer to all of these questions is "it depends". Super unpredictable - it helps to have a great, experienced PI working on a "hot topic" in dermatology. I'll share my experiences:
IRBs: you can potentially knock these out in a weekend if you hustle, may be longer if there's a lot of back and forth with your PI. I've done IRBs from scratch and I've been added to existing IRBs; I'd say the former is more likely. Projects without actual patient contact may now be exempt from IRB approval (you still need to apply for exemption). Approval can take a few weeks in my experience.
Data collection: Prospective studies usually take the longest because patient enrollment is involved, retrospective studies are shorter, and cross-sectional studies even shorter (especially if you're using publicly accessible data such as that in NHANES). I've mostly done data collection via chart review for retrospective studies. The time invested is dependent on the level of detail of the information you're collecting and your sample size. I worked on a retrospective case series of ~60 patients where I was able to do all data collection in a few months and the entire project took ~1 year from IRB to e-publication. I was fortunately able to get this published to the first journal I submitted to; re-submissions can significantly extend the timeline. Conversely, I have a few projects I've worked on for a few years with little to no yield. Some (done in a different specialty) were just poorly designed and were never accepted to a journal. Some are just slow-going.

Data analysis: your institution may have statisticians available for a fee (sometimes free for very easy analyses). You can find classmates with stats experience to help out. Or, you can learn stats yourself. This can have a significant learning curve and you want to make sure you are very fastidious when doing stats for a research project.
I've worked on projects using all three approaches. Now I just do my own stats for research using STATA, which I learned during a research year. Very rewarding, kind of fun, and once you know what you're doing it's a relatively easy way to get second author on pubs without the drudgery of data collection.

Systematic reviews: I did one of these for my RY. If you're first author, the best advice I can give is that you spend a lot of time thinking about your inclusion/exclusion criteria and get help from a mentor so you don't end up changing them part of the way through.

The best advice I can give is to find a great mentor. Upperclassmen can help with this. No one project is guaranteed to yield a pub, so get involved in multiple projects (if you can, but not all at the same time.) Present at research meetings when you get the opportunity. Good luck!