Is it possible to reach King of Games with Tier 3 and 4 decks?

You can with luck/#plays btw if it's below 120 games it's ok. Good deck take you to KoG<40 games but you still need to play other 80 games for rewards anyway. For me, it's easy to KoG at start&end of month

Hit KoG with my own duel standby Dark Magician deck.

I've been KoG for the past six seasons with Gravekeepers

no it impossible lmao

I hit Kog with tier 3 decks (dinos, AG) cause these are the only full decks I have as a f2p lol

It's wise to save your gems since meta decks stay strong for about 2 months at the most, so better save 'em so in the future you'll be able to invest 'em in building a solid amount of updated staple cards. As if your tier 3 & 4 decks will get you to kog currently it's difficult but possible, it wil depend on your ability to adapt your own deck to the decks you encounter the most, reading and therefore predicting your opponent's way of playing, reading his cards, and also in your own luck.
A little tip: if you want to rank up a little bit easier wait for the final stages of the season, you'll find mostly players who have reached their respective ranks with their full potential

Even this deck didn't listed in tier 3 nor 4, but it helped me to reach the KOG. So believe with your own deck and keep trying best to reach KOG

It depends on what you call "tier 3 & 4", but I'd say absolutely not. No matter how creative you are, once you run into braindead special summon decks that disable your spells/traps and even monster effects, like crowler decks, no amount of cleverness will save you, the only answer to those is to special summon harder. The closest thing to an easily available counter to the meta is Chaos Hunter, a card you can get from the trader.

I think they are, if you can hit legend with them. At legend you will run into 3 or 4 decks more or less. just put in some counter cards depending on your deck and it can work.

It's a hard struggle because they have spell and traps that can negate your tier 3 and 4 strategies. Maybe one day, if they add better spell/trap removal cards, but the playerbase keeps complaining that those cards are "overpowered."