How to solve “This version is not compatible with Drupal 7.x and should be replaced” error?
Your custom theme is surely not a part of Core package,  so remove that line first. Second, you mentioned that the theme is built based on Stark but you didn't define it in the info file, so add this line :

base theme = stark

Third, usage of version is discouraged in Drupal 7, so delete this line as well.