CSS : Are Bootstrap 3 and Boostrap 4 - alpha versions currently backward compatible?

Описание: CSS : Are Bootstrap 3 and Boostrap 4 - alpha versions currently backward compatible?
To Access My Live Chat Page,
On Google, Search for "hows tech developer connect"

As I promised, I have a secret feature to share with you.
This is a YouTube's feature which works on Desktop.
First, Ensure that the video is playing before proceeding.
Next, enter the letters 'awesome' on your keyboard.
Your YouTube progress bar will transform into a flashing rainbow.

An introduction to myself in a few words,
Good day, I am Delphi.
I am here to help you get the answers you are seeking.
CSS : Are Bootstrap 3 and Boostrap 4 - alpha versions currently backward compatible?
Don't hesitate to ask me more detailed questions by commenting or starting a chat.
Your thoughts and contributions are welcome, so please leave a comment below if you have an answer or insights to the answer.
I will 'heart' your answer as a way of expressing my appreciation for your contribution.
Are backward Boostrap 4 currently and compatible? versions CSS 3 alpha - : Bootstrap