I need to collect and use full name and some other basic information during registration, which is not possible wpforo lite. So i will redirect user to other registration link.

But for login and password reset, we need to use only email/username with password and only username/email respectively, which is possible with wpforo lite. 

So, if i user custom user redirection for registration only, and other two option left blank in wpforo setting, will it work??

Hope you understand me now..

Posted by: @civilenggnotes
I mean suppose, after registration and confirmation, user is redirected to their and account tab to complete the display name and nick name. Then they can use their profile for posting??

Or if i use another plugin for registration such as ultimate member, and use wpforo default login, or forgot password, will it work to show the display name and nick name??

 We don't follow you well, please try to explain in other words.

1. How to customize the registration form. I want to add first name (required), last name (optional), password (required), confirm password (required).

To customize the registration form I will suggest you check out the wpForo – User Custom Fields add-on. This add-on allows you to create custom Registration form with custom fields. To add a new custom field in form, just drag and drop fields from Inactive Fields area to Registration Form area. If you want more fields, please navigate to the User Fields Manager tab to create them.

More info here: https://gvectors.com/product/wpforo-user-custom-fields/

Posted by: @civilenggnotes

2. Change the form title from forum login to "login" only and forum register to "register" only.

All wpForo phrases are located in Dashboard > Forums > Phrases admin page. You can find and change each phrase as you like.

If you don't find the phrase, please, click the button, insert the identical English version of that phrase as Phrase Key and the translated phrase as Phrase Value.

Also there is an "Enable User Registration" option, please check it.

The option is locate din the Dashboard > Forums > Settings > Features admin page. More info here: https://wpforo.com/docs/root/wpforo-settings/features/#user-registration

Posted by: @civilenggnotes

3. I am also looking for a sidebar widget for login form with register and reset password link below that.

Please navigate to the Dashboard > Appearance > Widgets > Available Widgets section find the "wpForo User Profile & Notifications" widget and drag it to a sidebar to activate it.

Posted by: @civilenggnotes

4. Use of first name or display name after @ instead of user name. So that only the user and the admin can know the user names.

Please read this article. It should help you better understand about the difference between the Username, Display Name and the Nickname: https://wpforo.com/community/postid/17315/

4. Use of first name or display name after @ instead of user name. So that only the user and the admin can know the user names.

1. How to customize the registration form. I want to add first name (required), last name (optional), password (required), confirm password (required).

2. Change the form title from forum login to "login" only and forum register to "register" only.

3. I am also looking for a sidebar widget for login form with register and reset password link below that.

wpForo profile avatar and URL is integrated with wpDiscuz. So you can use just wpDiscuz and wpForo. If you need more integration points, please let me know.

TIA..