Originally Posted by chanchan05
...2. As mentioned above no, but you can use several apps to back up the apk file like AppMonster. This is often done so that when you don't like a particular app update, you can revert back. However this is different from manual side load by getting apk's from obscure sources. The apk's wont be tampered with by anyone. Note that you cannot backup app data unless you are rooted. But installing an older version to overwrite the new one should not be deleting any data anyway.
I backup all of my app data regularly and am not rooted. Most of the apps that I use now have the capability to save settings also, which I can also backup.