"basing on" vs "on what basis"

[jctgf]

hi,

1) are you basing on what to say this?

2) on what are you basing this/that?

3) you are basing that/this on what?

4) on what basis are you saying that?

do all the sentences above mean the same? are them all good and natural English?

thanks,
JC

[Tdol]

1 doesn't work. The others are OK, though 3 is fairly colloquial.