A few questions about keeping kosher

I would like to start by saying I am not jewish, I am however looking to begin converting next year (after I turn 18 and live closer to a temple).

I know that jewish people don’t celebrate easter as it is a catholic/christian holiday. Commercial food things made for easter/other non jewish holidays that are marked as kosher (like the mark saying that something is parve, etc). Can a jewish person consume those if they are actually kosher or are you not supposed to do that?

Is it offensive for me to attempt to start following kosher rules before I am officially considered a jewish person?