Dev pls buy back all available coins on exchange to raise the price please. I have invested my everything in this coin. It will give me a big shock if price doesn't recover

This never happens.
You can't expect a dev to pour in a couple of btc and even if the dev does this, there is no way the price will remain stable as long as the dev doesn't put up a 100 btc wall on all exchanges.
People in crypto need to stop dreaming, things like this happen and no dev will buy back coins.
They create the coins for you to buy, not so they can buy their own coins.