I am using 2.4.5-rtl2 version of modular, I was trying to change the theme with existing one but unfortunately I can't apply this theme to work properly with this version 1) The width of popup windows becomes larger. 2) This theme is only working with LTR not with RLT language.
The rtl version indeed contains a specific theme to support the right-to-left situations. If you want to have another theme you should take the existing theme as a starting point. Theme's for the 2.4.x release won't work for the 2.4.5-rtl releases.