As far as I know, The fuse being the link is acceptable (I do this with my ants and have designed it into my feather) so long as removal renders the robot dead you should be fine, and the rules stipulate that it must be removeable by hand and without tools, there are many using things to hold them in like straps and things, nothing says you can't. I have a brilliant bayonet fitting that I plan on using if I can make it fit.

Although for the fuse, is that a fuse holder? I use a pair of insulated female spade connectors as I find they tend to stay tight for longer, maybe a thought for the next build.

2S lipo might leave you a tad sluggish, but you should be fine, if anything I prefer a bit slower as my driving is a bit... pants...

Just make sure the battery is well protected, bit of foam to stop it rattling about as a minimum, and I think you should be good to go! If you have any serious concerns you could try to contact the Event Organiser directly and ask them, they can give you the definitive answer for a particular event.

Looks a decent first build and I wish you luck in the first event!

Finally, WELCOME!!!!!!!