I can not give you any garantee. ^^;
(you may need new topic about how to up-date ds 4.6 from ds 4.0 safety,to get many advice in forum menber,,
I should ask many things if I were you ^^; understand your feeling clear.)
I think we can install only one daz studio 4 in same PC,, (and it is recommended)
so that you must need to un-install ds 4.0 , to install ds 4.6 (or beta)
(though we can install ds 4.6 and ds 4.6 beta,, but I do not think, we can install ds 4.0 and ds 4.6 beta
and it caused many problems for me before)
But up-date to ds 4.6, means just un-install aprications (and plug-ins buillt in contents for ds 4.0 only) clean
then install new ds 4.6 , CMS, and plug-ins for ds 4.6.(if they have been version up - ed for ds 4.6)
if you get free plug-ins which offered for ds 4.0 , about some plug-ins may not work as you expected.
The important things is keep clean un-install by installer (if they has been offered ).
about aprication (daz studio 4.0), CMS, and buillt in contents. then re-install by DIM all you needs correclty.
if you have same plug-ins which made for diffrent version,, un-install old and install new for ds 4.6 only.
may need set-up again about some plug-ins.
Actually As for me,, it was not so easy up-date to ds 4.5 from ds 4.0. (almost two years before,, I think ^^;)
Basically most of items which you used in ds 4.0 , and scene, preset which you saved in ds 4.0 can be used in ds 4.6
as same as before.
about dsf preset files which you saved in ds 4.0, you may use them without problem.
But you can not use duf files ( saved in ds 4.6) in ds 4.0 again. so that you may better copy directories
which you saved files for ds 4.0, as different name,, then keep them safety.
Eg about some original saved scenefiles (.daz),
When I opend some .dsz scene files in ds 4.5 then save them as duf,, I found problems,,
but re-save them again as duf,, usually it remove problem ,,
I can not say ,, you can use all files which you saved before without problem.
But after you set-up correctly,, it must offer you many advantage,,,,As for me I can not think to use ds 4.0 again,,
Then you may better to ask all about which you feel worry to daz support one by one.
(or ask user who recently up-dated to ds 4.6 in forum. then try to set-up one by one. with correct step.)
not all, but some user may found difficulity to up-date ds 4.6 and set-up correctly,
And I do not know, at current,, we can get old daz studio 4.0 version when you need,, , from daz
(though if you have CD or old installer or zip for each (bullit in contents, ds 4.0, or plug ins)
it should work,,