I am new to Envato. I searched for " Can I Sell on graphic river & codecanyon under one account" I found that we can sell on both under one account. but I have questions
what are the limitations & conditions if I can sell on both sites like graphic river & codecanyon under one account?
No limitations - you just have to make items suitable to each marketplace.
There are restrictions on being an exclusive or non-exclusive author and selling items on just envato marketplaces, or elsewhere too https://help.author.envato.com/hc/en-us/articles/360000471226-Exclusivity-Policy
No, there is No Limitation.