1. is there any difference between Reader Mode, Transitional Mode & Standard Mode SEO wise. will i get More seo benefit if i move to full AMP (Standard Mode).
We don’t have advice regarding SEO. We advise regarding performance. But if mobile visitors get improved performance due to AMP, then that should be a positive indicator in terms of SEO since performance is a page experience signal. See https://webmasters.googleblog.com/2020/05/evaluating-page-experience.html
2. Suppose if i am moving from standard Mode to Reader Mode will there be any issue like redirection errors or SEO wise is it not favourable.
When switching between the different modes, the canonical URLs will not change. The way that the AMP plugin does redirection is implemented according to the Google Search docs on Separate URLs: https://developers.google.com/search/mobile-sites/mobile-seo/separate-urls#automatic-redirection
3. Is there a way i can get divi shortcodes to displayed in Reader Mode themes.
I am unsure. Does Divi put the shortcodes in the theme itself? If so, then that is problematic for Reader themes since the theme as a whole is switched during AMP responses. If the shortcodes can be moved to a plugin then this would ensure they work in both the active theme and Reader theme, or any theme you switch to in the future.
