I've borrowed a friend's mtb so I could take the boys on a couple of runs (Sherwood Pines and Cannock Chase). The price of the loan is making it ridable.
The front tyre was flat. That'll be the 1/2" thorn in it. No: your slime (which has nicely coated the inside of the tyre like hard, dried snot) will not work if you leave the thorn in.
The front mech doesn't move. That'll be the accumulated dirt. If you don't have mudguards (and even if you do) and you don't clean it sometimes, that's what happens.
That clicking noise is the headset. If you can hear that, then it needs adjusting. Or, probably, given everything else, by this point, replacing.
Those saddle rails should be straight.
I've got the bike ridable. Then, yesterday evening, the school contacted me to say that Louis has to self isolate for 14 days, so the ride's off anyway!