Migration from dojo1.4 to dojo1.10

Hi Dylan and team
we are planning to upgrade/migrate our dojo1.4 based bank project to dojo1.10, to resolve few accessibility issues.
Could you please help us in answering the following questions…
first of all , is it possible to migrate from 1.4 to 1.10 directly.

if yes, How much it effects our current application? do we need to rewrite/revamp whole code… could you please let us know what all things we need.

if we rebuild whole app on dojo1.10 from scratch, is it better way?

Check this answer