Hi
The applications are available in September and are due in November. So at the beginning of your senior year, you'd get an application in September and it would have to be back to the AB office in November (like around November 15th). If you take the MCATs in April of your junior year, yes...you can apply for the five year programs. It's actually better if you take the MCAT in your junior year or the junior summer cuz you'd get the scores by October. However, you should email the AB office about how closely they stick to requiring applicants to have an undergrad degree in a science major. I don't know if they Only accept those who earned Bachelors in sciencey majors, or whether they also accept just anyone with any degree but has completed the US premed science pre-requisites.
You should also email them about what they stress. I only say that they might value research experience because on the actual AB application, there is a specific section that asks whether you have done research, and what you've done/published. I don't know if it's considered compulsory. They'll probably like to see volunteer experience too, but I'm also not sure because students intending to go into medicine (they'd be high-school age) do not usually do volunteer work in hospitals. Their hospitals actually don't really have volunteer programs set up. I didn't have any clinical volunteer experience, I volunteered by various tutoring positions. However, I'm sure it'd help. Ask AB how much the irish schools value research. For trinity especially...academic research is pretty prominent in the school.
I graduated with a 3.7 GPA (magna cum laude) as a triple major earning BA's in Biology, Psychology and Classics. So I had the science major in there but also non-science stuff. I don't want to say my MCAT score, but it was on the lower end. Just good enough to get into US schools, but not as high as I would have liked. I attribute that to a combination of not studying as focusedly as possible (my senior class schedule and training schedule was really hectic) and being away from basic sciences for a year. When I did my junior year abroad at Trinity, the science courses were not compatible so I ended up only doing psychology and classics that year, and leaving all my biology courses til senior year. I can't say that was the smartest thing to do. I have pretty good, more unique EC's: research (with minor publications not as first author), rowing, JYA already at Trinity, writing for my campus paper as well as editor positions, membership and officership in national and state classical (dead languages) leagues, and tutoring for AOL ... and a couple honor societies/faculty committee positions.
Each applicant brings something different and varied to the pool, so it's kinda hard to say who makes it and who doesn't.
BEST of luck
It's really good that you're starting to research all this stuff way in advance. And it's cool that you're genuinely interested in another experience
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