Burning DVD, Booktype, Error checking program [v2]

1) I wonder if I should use a DVD- or DVD-RW in the following situations.
Eg: I burn a film or music. Is it necessary I need to close a CD/DVD before it can be read by a DVD standalone player?

2) How about if I clone a CD/DVD, is it necessary I have to close the CD/DVD?

3) What does a booktype do? It seems it is used to change the the disc type. But what's the point of it?
And if I change the disc type to either DVD-ROM / DVD-R, will this close the VD as well?

4) Is there any program which can check whether the burnt CD/DVD is REALLY error-free, or burnt properly?
I once experienced the burning program said the CD was burnt successfully. In fact it couldn't be read by others.

5) Is there any program which can check whether files (in my computer) is error-free or readable or uncorrupted?

[v2] 6) Which types of DVD should I buy, plus or minus?
Why?
I will burn the DVD and be read by both DVD standalone and computer DVD drive.
I will also format the DVD as UDF which can be accessed as if it were a floppy disk.

Thanks.