(adsbygoogle = window.adsbygoogle || []).push({}); Hi, I have read a little but about the 4.21cfw but not to the point of doing anything
I have some questions about this

Is it recommended to upgrade to 4.21cfw?
What are the advantages of upgrading?
Can I go from 3.55 kmeaw right to 4.21 cfw?
If I do, Can I go back to 3.55 kmeaw?
Is and/or will there be playback of 4.21 and/or below eboots?