Can we negotiate with a rejected offer?

Is it a good idea to accept an offer after declining it? Have any one of you ever rejected an offer because of some concerns with that company but after around a month you realise that the company and the compensation offered was good and you should have gone along with them. So is it a good idea to mail them regarding the same and ask if the offer letter still holds?

I got to know that budget for the role i interviewed is in range of 20-25 LPA. My last drawn salary itself is lower than the market standards. The company wouldn't give hike more than 30% considering my experience in the role domain. But I have performed well in all my interview rounds. Any tips from the community to negotiate for atleast the lower band of their budget?

It's been a month now accepting the offer letter, only 15 days remaining till I join the new company, can the recruiter now decrease my compensation again if he knows my company is going to do a layoff round?

Hey Guys! I am new to the corporate world and am not familiar with all the nuances, is it okay that you change your mind during the notice period and decline an offer post accepting it from another org?

What can be the consequences of showing Forged offer letter. Like I have got offer 0f 24LPA from Company A. Now company B offers me same I want to join B, whatif I edit 24 of A to 28 LPA, show that to B and ask them match it. I don't think B will contact A to confirm it, BgV also concerns previous employers.. So is there any risk???

I got the offer letter from accenture today just 1 day after the final interview discussion. I did not had any HR round related to compensation. The compensation is too less than what they had told in the first call. What should I do now?

I got an offer, I knew the role was not great but still went ahead to see if pay would be better (75% up). But I still would like to try for a better role and not accept this. I need your suggestion on how to do this, so that I won't be blacklisted for future opportunities of the offered company.

Once we accept multiple offers, how and when should be reject them before joining in a good way? And do companies blacklist if we reject the offer after accepting?