I am using opencart 1.5.6.4 default theme for my web. Based on Google analysis, my e-commerce website is now not mobile friendly yet. I have upload products and the web has been launched online for years. My priority is everything -- products, pages, etc -- remains the same, while adjusting my web to a mobile friendly one.
1) Could I change my web to mobile friendly, just using css? Means, I design a css file to manage picture max width to 100%, textbox max width to 100%, remove auto correct, add viewport to 100%, change background size to contain, and something like those. Then I just need to link css file to my web pages. And the css file then change my web into mobile friendly.
And if I can not do that, can I just change add css one by one to my theme in www\catalog\view\theme\default\template to adjust my webpage to a mobile friendly one?
2) If I can not do point 1 above, I think I will need responsive theme or mobile friendly extension.
For this purpose, do you think it is better use responsive theme or extension/plugin?
If I should use extension, I would prefer the extension can use vqmod, so it would not change codes or settings of my webs, just change on the fly.
My requirement is that it is compatible with my 1.5.6.4 opencart, and it was built based on 1.5.6.5_rc version, hence it also get 1.5.6.5_rc security fixes inside it.
4) If I should use responsive theme, what should I do to make my web mobile friendly, while maintain the contents of my web? Should I just install the theme online to my web, then check the pages one by one, and adjust its if some pages don't function correctly?
5) I have upload many products in my web. So how can I make my web to mobile friendly one, without discard the products I have uploaded?
Does changing template only is enough, so I don't need to change the product database, hence my products do still exist when I change my web?
6) Is there any analytic tools that can scan my offline files to check whether my web is mobile friendly or not. Because I am going to use offline backup to adjust my web to mobile friendly, and just when everything works perfectly I am going to upload my offline works to my online web.
Design (HTML+CSS) will not effect on your database. You can use responsive theme to make website mobile friendly. Make sure take complete backup of website before applying new theme.
Note - Custom changes or vqmod can effect your new theme.