It says molecules, not cells.

Both, but heavily depends on the molecule and the cell. The question is more nuanced, so unfortunately so is the answer, cuz the body is so complex there's rarely a straightfoward answer.

But if allowed to overgeneralize, most of it goes inbetween and "through" the wall that the cells make.

Are u asking about mechanism of action? Because it's the same as most nsaids.

If ur asking about absorption, topical application still gets absorbed. Your skin (keratin mainly) is hydrophobic, so it resists water and other charged substances from entering, but there is a hefty list of chemicals that, if touched, can be absorbed into your bloodstream and even be toxic (notable, methylmercury, as only a tiny bit is touched is needed to be lethal, the methyl means it has extra carbon and makes it more like an oil and bypasses the skin's hydrophobic effects easier).

Hydrophobic stuff will resist charged particles, such as water, from interacting, but will allow other hydrophobic stuff, such as oils and anything thats mostly carbon, to interact. For instance, pure lead (a metal, so its charged) isn't that toxic unless u inhale or ingest it, as the skin works well to resist it. However, tetraethyllead (lead with extra carbons) is very toxic via touch.

(Small edit for clarity, oil actually doesn't get absorbed that easily, as its a big molecule, but its the most easily recognizable hydrophobic liquid, so it was used as an example to make the concept easier to grasp. Just wanted to clear that up).

Read a book

No one's born with natural immunity to it that we know of.

I have type O+ and got super sick. (Was double vaccinated)

The blood type and covid study has been debunked countless times.