Using Recaptcha v2 and Guest Entries plugin How can I prevent bots from sending tons of messages from a frontend form, it uses the Craft Guest Entries plugin. I'm using Recaptcha 2 but it only hides the submit button and it doesn't work using Craft 2. 

All other solutions (antispam) that I check seems quite old...

Thank you.
I don't have much experience with these, but here are some potential plugins you can look into for Craft 2 that use various anti-spam techniques:

https://straightupcraft.com/craft-plugins/snaptcha

https://straightupcraft.com/craft-plugins/sprout-invisible-captcha

https://straightupcraft.com/craft-plugins/google-recaptcha

https://straightupcraft.com/craft-plugins/spam-guard