Can we do client side validation on vCAC catalog page?

I am using vCAC 6.1 with vCO 5.5.2 GA builds.

I have set of custom properties which I have defined in "Property Dictionary". For all the properties control list is "DropDownList" and all are required fields.

Using vCO workflow, this drop down list gets populated from database with extra option as "Other".

Now the problem is, if user selects "Other" option, which indicates user doesn't want to select value from Drop down list. So if I compare this with HTML client side validation then I have 2 options,

1. New text box should be appear for entering value.

2. While designing I'll add child property for each drop down list with control list as text box and optional. So if user selects "Other" option then usermust enter some value in given text box and this text box will be required field.

So I would like to know,

1. Is it possible to do such client side validation?

2. Is it possible to customize vCAC request page UI?