the bottom two challenges, you can do from the portal. There are set portals already set up to help in this matter. Watch YouTube Bman videos, he has a couple of codes to help you out. I find that playing both the Bot and normal games, that you can get some of these. But if you want it easier, then the portal can help you out. Although the 6k repair is a long slog. Only way I did this was you literally need carry the av grenade - to help damage as some of the lobbies need a lot more luck or patience :) Good thing on the portal set up to help on the repair one, as the vehicles tend to congregate around the points to capture, crawling under a tank was best way, praying you're not flattened :)