To remove the "Custom TAB -1"
1- Open Joomla Plugin Manager and find this plugin: "Flexilbe VM2 Template".
2- Find this field:Custom Tab-1 - Title:
3- Remove the field.
4- Hit SAVE.
5- The "Custom TAB-1" tab will be gone.
To remove the Select a Product Variant first button
If you use "Generic Child Variant" custom field, then it is normal that you will see "select variant first". Because the "parent" itself is not orderable, you need to select the "child" from the drop down select box and add the "child product" to cart.
If you don't use "Generic Child Variant" custom field, you won't see the "select variant first" button. Instead, there will be only "add to cart" button.