I'm planning to clone my N810. But first i need some answers on a few questions.

1. What is better clone to external SD or internal. (i expect with external you can backup and maybe put it into another N810 ?)
2. Do i clone or can you get the same apps with debian Chroot? Which installs on a external sd card
3. Is cloning foul proof. I read the deb and it sound easy enough for me to understand (basic linux )
4. DO i first need to clear everthing on my Flash before doing a clone. I just installed every nice app. (ofc i want more in the future)