I did not yet look at the file, because there are/were other issues to address first but I'll get to that in a moment.

The htaccess file provided in the download would go into the temp folder used for file upload/download. There are other reasons not to incorporate it into the main htaccess file of the admin. The file is intended to control/limit access and such permissions are best to be applied at the point(s) where they are needed. Because this plugin only needs to access csv files in the temp (or otherwise named) folder, that folder is the only one that needs the extra rules of the file.

Now, back on the import file. It is possible to use EP4 without products_model, but it is not the default functionality. One of the first/early instructions describe that this plugin uses the products_model field as a primary key.

So what's a primary key? Think of it this way. You live at an address, your address is different than everyone else's. In order to find your house you can either provide the address or you can give very detailed directions that only someone while in the "area" can follow like the big tree on the corner, or the red house on the left. Computers don't tend to do well with the second part, but if enough data exists, it can be done. Anyways, the address of one's house is similar to products_model for EP4. It's the one "unique" piece of information that says hey, this line of data belongs with this product. Now, ZC as a database program uses products_id as the primary key. This option has been added to EP4, but, one should also realize/consider the source of data to populate the database. If it is your own entered information (not from some mass import vendor file), then go ahead, use the products_id or blank_new option (I suggest blank_new if you are not going to hard code the products_id), but even so, you don't want to end up with the same exact product listed more than once as a primary product. It can be linked, but you don't want the same product multiple times in the products table it's not good for ranking and would likely cause an inventory tracking issue.

Anyways, that's a lot of information again. The general process is straight forward. Start with one thing at a time, then work your way to many/multiple items and things. The requirements are provided in the instructions, it's how they are applied/uniquely used that makes this tool something to do things faster. There *is* a learning curve to overcome to gain the most benefit from it and "daily" business.