Is flagging ok ??

Well in my blitz games it often happens that my opponent gets a decisive advantage or maybe even goes material up but still couldn't convert as he is simply low on time and I just use it to flag him. I don't even care to defend properly, I just make random quick moves and that's it my opponent loses before finding a way to punish me. I know I will get punished if I reach higher ratings but at my level it just works pretty well. So now my question is, should I stop doing this as it's against the sporting spirit??( I mean just resign in that position) or it's just ok since win is the only thing that matters. Also if possible leave a suggestion on how to find the winning idea quickly as that's the problem with lower rated players like me cuz' its it's really hard to find the winning idea quickly which results into losing on time. Anyway thanks! if you care to answer my question and sorry if you had any problem in understanding what I meant to say as my English is not that good.

I think it is okay in blitz and bullet, but not a good thing to flag opponent in drawn position in rapid time format.

You and your opponent get the time on your clocks to do as you see fit. Including in rapid games. If you can win by getting them to flag, then that’s part of the game, and you’re allowed.

Of course it’s fine. That’s a part of the game.

Never resign in blitz or bullet, ever.

I’ve lost games where I had material advantage and an increment (or maybe I’m just stupid), but I’m still not going to resign unless it’s rapid.

Some months ago, chess.com moved where the resign button was and I was stuck in a terrible game still playing moves long after I tried to resign. I made apologies to my opponent afterwards.