I would like to know why its recommended Firefox for Oracle 12c form . Why not microsoft edge or google chorme.
Firefox is not recommended for Forms, who told you that?
It's not possible to run Forms in Firefox, because it no longer runs Java applets.
IE11 is the only browser left that can run Forms.
Use the Forms standalone launcher (FSAL) instead.
Slight correction to cormaco comments.
You can use Firefox, Chrome, Internet Explorer 11, or Edge. However, IE11 is the only browser that supports using the Java Plugin. So if you want embedded applet you would need to use IE11. If you don't care about embedded applet you can use any browser, but using the Java Web Start configuration. Of the three remaining browsers (FF, Chrome, Edge), Firefox offers the best user experience (in my opinion) when running Web Start applications.
Longer term, consider transitioning to using FSAL.
More information about all the Client Configurations and specifically FSAL can be found on the Forms 12c Tech Listing page on the Oracle.com web site.
user10606619 you information is not entirely correct.
1. Java Script integration support can be done with Forms 18.104.22.168. Refer to the latest Forms 12c New Feature Guide (and Deployment Guide)
2. Internet Explorer (Microsoft) is planning to continue supporting IE11 through the life of Windows 10. Exactly how long that will be depends on exactly which build you are using. In some cases, that will be out into 2029. Refer to the MS documentation for the latest information on Win10 support dates.
3. You are correct in that SSO is currently not supported with FSAL. However it is supported with Java Web Start. It is also planned to be re-introduced in a coming version of Forms.