Savedatafiler is a dev signed CIA file - hence the "can't install" because you're not using a dev unit (if you were, you'd only be able to install dev signed apps and not games etc).
There's a "properly signed" cia version which will install on retail consoles fine (I've still got the older version installed on my N3DS XL), but JK's Save Manager is leagues better than Nintendo's own offering (among other things, it allows you to restore "time locked" save files (ala Pokemon or Animal crossing) which Savedatafiler wouldn't allow (you'd get a corrupt save)).
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You'll have to give more info here.
By browser, are you talking about viewing the Decrypt9 page on your PC [to download it]?
By "other 3" are you talking about options within Decrypt9 or on the guide?