Yes, you can edit and repost / update it.
But, you can't get rewards as usual, if your post is already get payout (after 7 days).
There are various apps like esteem/surfer which allow you to post on the steem blockchain through their interface. These apps have more features than steemit.
One of these interesting features is editing the posts after the payout is over.
Though these enhanced apps can allow editing after 7 days, typically they can not permit payout beyond seven days as it is the inherent limitation of the steem blockchain itself. Hence editing after seven days is a feature in various applications but extending payout beyond seven days is not possible
Thanks for your good question.
An old post in steemit can be and can not be edited and reposted. It can be edited and reposted if the post age is not more than 7 days. And it can not be edited and reposted if the post age is more than 7 days.
Steemit is online earning site where can earn cryptocurrency by blogging. There are many platform in steemit where we can contribute and earn cryptocurrency. We get our post reward after 7 days and in this 7 days we can edit our post if there is any problem and repost it. But we can not edit and repost our post when the post age is more than 7 days.
If we can not edit and repost our post when it is more than 7 days then it is very easy that we also do not earn reward as usual. We all knew that we can earn reward from our post once when the post age is 7 days. You and anyone can upvote your that post which age is more than 7 days but you can not earn any reward.
As i do not use any kinds of steem related apps so i do not know about them. There may be some feature by which we can edit and repost ourn post which age is more than 7 days.
After the recent Hard Fork (HF20), posts after 7 days can now be freely edited in Steemit.com and other Steem platforms.
As for the rewards, unfortunately you will not get any. However there is now a way to still get some rewards from a post posted beyond 7 days, this new initiative is called Steem-Bounty Service Forever. This new service will allow all upvotes on that said post to be rewarded back to the author by Steem-Bounty making a comment under that post and setting the author as 100% beneficiary.
Visually, it will look like this:
All you need to do is simply change the url from steemit.com to steem-bounty.com:
Using the same link as the image above that would be: