First of all you can add 3 images as your portfolio, after getting order delivered order automatic add on your portfolio as permitted your buyers, When you get more order fiverr give you a feature for add a special portfolio. This is the complete process as I know. thanks.
Now fiverr hasn't buyer request system, Only have brief system, you can edit your gigs with best quality description, fiverr will promote your gig and possible to get new order.
Your content doesn't comply the fiverr terms and conditions that's why happens this type of issue. You create your gig by self content hope that will approve.
Yes, You can do that, also I'm telling my buyers, I have completed your project can you please check this, after your confirmation I'll deliver the project and accept the order.
You must get the exact point what actually buyer want, then you write the excact point which you provide. must be write simply not complicated. thanks.