@guhanath I found this extension that was helpful for me. Hope it helps you too:
https://chrome.google.com/webstore/detail/disable-automatic-tab-dis/dnhngfnfolbmhgealdpolmhimnoliiok
Apparently Opera automatically discards inactive tabs, but in my case and yours it's discarding active tabs too. Anyway you can go to opera://discards to see which tabs are discardable and toggle them on or off. With this extension for me none of the tabs are discardable anymore.