Hey
I'll try to answer your questions to the best of my ability, but without certain pieces of context feel free to interpret my answers in a manner you see best fit.
For the first question: the extracurricular activities should not be something exactly related to your desired course. This is because the purpose of extracurricular activities is to highlight to the institution your interests and qualities as a candidate. It does not necessarily mean that if you are going into the medical field of study your extracurricular activities should just involve volunteering at a hospital or daycare. Something as seemingly unrelated as running for the position of student ambassador is a good extracurricular activity to be involved in because it shows your ability to work in a team, your communication skills, and your grit at balancing student responsibilities with ambassador duties. Although, yes volunteering for a hospital would be a great extracurricular to highlight in your application as a medical student it is not the end all be all of the extracurricular activities, there are other options to navigate that can give you similar experiences.
For the second question: the best way to narrow down college choices is to categorize them into three main choices. First would be your dream college, this is the one that you are essentially working your hardest to reach and would do anything to be enrolled in. Second would be your last resort college, although this may sound a bit harsh you need to have a college choice where if you do your absolute worst in school, you can still manage to squeeze yourself into that college fairly reliably. And finally the mid-college, this is the college that if you do the absolute bare minimum and just go about your school days just aiming for a passing mark you would have enough marks to get you enrolled. As for the chances of you getting into college, it is slightly complicated to answer because this is completely dependent on your school performance and the expectations required from you by the university of your choice. But generally speaking, your selection of colleges will definitely affect your chances of getting in because if you are applying for a college in the hopes of being accepted despite not meeting their base requirements you might be disappointed with the results of that application.
I hope this helps!!
Derrick