Hi,
1.a. In the "symbol" field of the currency, you can enter HTML code. So you can have an img tag with your svg file.
www.hikashop.com/forum/4-how-to/10569-ch...currency-symbol.html
1.b. You would have to modify the line:
$this->values[] = JHTML::_('select.option', (int)$currency->currency_id, $currency->currency_symbol.' '.$currency->currency_code);
in the file administrator/components/com_hikashop/types/currency.php
Please note however that you would loose the change each time you update your HikaShop so you would have to redo it.
2. It's an option to change the way the module works. Either with a real HTML form, or with a URL redirect with extra parameters in the URL. Both work fine normally. However, based on how you display the switcher module on your website, it's possible that the form mode wouldn't work (for example, if you add the module inside another form, or if you have javascript errors on the page.
If your switcher module works fine, no need to change that option.
3. It's probably a problem with the CSS of your template. Without a link to that page, in order to check the CSS, I can't say more.
4. There is no option for that. The only solution is to export the hikashop_currency table from your phpmyadmin as a CSV. Edit the CSV in Excel, and change the order and id of the elements the way you want them. Then, empty the hikashop_currency table in your phpmyadmin and import the modified CSV in order to get the currencies in the order you want.