What’s your opinion? And why? 

I think you should at least have partially seen it. Skipping through some parts is ok. But it's way more fun with the context knowledge in my opinion...

Yes watched the 1st n 2nd sequel will make you understand the jokes better

Yes. I expected no less. It's like jumping into the middle of game of thrones or vikings. The story is a continuation of the characters. in this show its even more important. this couple has gone through a lot of times and places with each other. I love the gender equality switch in this 3rd season.

it is not necessarily, since every season has different timeline and plot.  only the main characters and some supporting charas that remain the same. the 3 seasons were linked by time leap story of the chara. 

anyway, if you watch the previous seasons, that would be  good too to get better understanding about the main chara story!

 Srujan Srujan 36:

• But if we watch the first two, it is of better understanding and obviously we watch the dramas for a temporary peace , right ? So all we have to do is just have to watch 60 episodes before watching the 3rd season, it would take not more than at most 1 week.

I wanna to explain like this:

Detective conan anime have countless episodes. but I can still watch random eps because every episode has different case/story to tell that usually does not relate to previous eps.  Only the casts (Conan and his companions) remain the same. 

And if you curious about Conan and Ai Haibara, for example, if necessary you can dig previous eps that tell about their past history.

From what I understood the original poster was enquiring about a specific series - The Eternal Love 3 (2021) and its prequals The Eternal Love (2017) and The Eternal Love 2 (2018) - wanting to know if they had to watched 1 and 2 first to enjoy 3.  For this specific series if feel that it isn't necessary as they can each be enjoyed and understood independently. However, having watched all three, I feel that watching ETL and ETL2 before ETL3 does enhance the enjoyment of TEL3.

When it comes to other series I feel that it is highly dependant on each individual one that you are considering.  In general we can say that the more you know/understand the better the enjoyment but in some specific cases it is essential to watch in sequence to understand/enjoy while in other cases it is not.