>>>>can i check if all are set to by layer in a quick way
Select all objects in the drawing and look at the Properties Inspector - you will see Color and Linetype property for all selected objects - make sure they set to "ByLayer"

If you select more then 25 000 objects, then you won't see information in Properties Inspector. In this case you can select one part of objects, then another part.
Or set PROPOBJLIMIT System Variable to 0 (zero) to be able to see properties of all selected objects. But keep in mind that this could affect AutoCAD performance, the default value for this Sys Var is 25000.