Whats your opinion about Div4

I don't think a div 4 contest is necessary. Beginners can attempt 2-3 problems in a div 3 contest and 1-2 problems in a div 2 contest. Div 4 will be a speed run rather than a learning opportunity.

Yes it is not very necessary. But, it will be fun.Will be more contests

I don't think a div 4 contest is necessary.

I agree: it's not necessary, insofar as Codeforces can do without it. However, that doesn't justify or provide any logical explanation for keeping/removing division 3. Plenty of actions are unnecessary, but still beneficial and contrarily, a plethora of undertakings are necessary but not beneficial. But alas, I digress :-)

Div 4 will be a speed run rather than a learning opportunity.

I agree: Division 4 will be a speed run for people who are sufficiently high-rated. The same applies for other contests too: for most div1 contestants, division 3 is a speedrun. For LGMs, most division 2s are a speedrun too. However, that doesn't mean that division 2/3 are useless: they're quite educational for people who are lower rated. That is to say, just because a division is a speedrun for a subset of people does not imply it's useless: it can very much be insightful and interesting for lower rated peoples.

Beginners can attempt 2-3 problems in a div 3 contest and 1-2 problems in a div 2 contest.

As someone who used to a pupil, it's incredibly demoralizing to solve only 1 or even 2 problems. 2 hours and only 1 problem? Furthermore, recently, there's been wide difficulty gaps in div2 between A and B, so only a very small subset of problems are even interesting for pupils/newbies. There would be a larger subset of solvable and therefore interesting problems for pupils, if there were division 4s.

Problemsetting

Writing a division 4 is a somewhat easy task, since most problems will be <= 1700 anyways. At least, I suspect a division 4 can be held every 2 weeks, and that it wouldn't strain problemsetters.