1. I don't think that there's any limit on the number of SIMs that you can order (they are free) for recruiting others. Definitely you can order up to 5 in one go from the Recruit page of your My48 account.
2. I'm not sure if there's any limit on how many minutes you can convert to data. But then I don't know if/how the fair usage limit works if you do what you're suggesting. You might need to ask 48 support for clarification.
3. In an earlier post it was mentioned that the €7.99 offer is for life but I don't know if that means that it will never change in price or terms/conditions. All providers reserve the right to unilaterally change the terms and conditions in the small print.
4. What do you mean by "log friends".
Hope this helps.